{ { Short description|Area of mathematics } }
{ { About||the kind of algebraic structure|Algebra over a field|other uses } }
{ { Pp-move } }
{ { Pp-semi-indef } }
[ [ File : Quadratic formula.svg|thumb|The [ [ quadratic formula ] ] expresses the solution of the equation { { math|1= '' ax '' < sup > 2 < /sup > + `` bx '' + `` c '' = 0 } } , where { { mvar|a } } is not zero , in terms of its coefficients { { math| '' a '' , `` b '' } } and { { mvar|c } } .|249x249px ] ]

' '' Algebra '' ' ( { { Lang-ar|الجبر } } { { Transliteration|ar|Al-Jabr } } , { { Translation|'reunion of broken parts ' < ref name=oed > { { Cite encyclopedia |url=http : //www.lexico.com/definition/algebra |archive-url=https : //web.archive.org/web/20131120000000/http : //www.lexico.com/definition/algebra |url-status=dead |archive-date=2013-11-20 |title=algebra |dictionary= [ [ Lexico|Oxford Dictionaries ] ] UK English Dictionary |publisher= [ [ Oxford University Press ] ] } } { { Cite web |url=http : //www.oxforddictionaries.com/us/definition/english/algebra |title=Algebra : Definition of algebra in Oxford dictionary British & World English ( US ) |access-date=2013-11-20 |archive-date=2013-12-31 |archive-url=https : //web.archive.org/web/20131231173558/http : //www.oxforddictionaries.com/us/definition/english/algebra |url-status=dead } } . < /ref > or ' [ [ Traditional bone-setting|bone-setting ] ] ' } } ; < ref name= '' CRC Press '' > { { cite book |last1=Menini |first1=Claudia |url=https : //books.google.com/books ? id=3mlQDwAAQBAJ & q=bonesetting+algebra & pg=PA722 |title=Abstract Algebra : A Comprehensive Treatment |last2=Oystaeyen |first2=Freddy Van |date=2017 |publisher= [ [ CRC Press ] ] |isbn=978-1-4822-5817-2 |language=en |access-date=2020-10-15 |archive-url=https : //web.archive.org/web/20210221075950/https : //books.google.com/books ? id=3mlQDwAAQBAJ & q=bonesetting+algebra & pg=PA722 |archive-date=2021-02-21 |url-status=live } } < /ref > { { IPA| [ ʔldʒbr ] } } { { pronunciation|Q3968-ar.wav|listen|help=no } } ) is the study of [ [ Variable ( mathematics ) |variables ] ] and the rules for manipulating these variables in [ [ formula ] ] s. < ref > See { { harvnb|Herstein|1964 } } , page 1 : `` An algebraic system can be described as a set of objects together with some operations for combining them '' . < /ref > Originating in ancient [ [ Babylonian mathematics|Babylonian techniques of calculation ] ] , it is now a way of thinking that appears throughout almost all areas of [ [ mathematics ] ] . < ref > See { { harvnb|Herstein|1964 } } , page 1 : `` ... it also serves as the unifying thread which interlaces almost all of mathematics '' . < /ref >

[ [ Elementary algebra ] ] deals with the manipulation of variables ( commonly represented by [ [ Roman letters ] ] ) as if they were numbers and is therefore essential in all applications of mathematics . [ [ Abstract algebra| '' Higher '' or `` abstract '' algebra ] ] , which professional mathematicians typically just call `` algebra '' , is the study of [ [ algebraic structure ] ] s that generalize the operations familiar from ordinary [ [ arithmetic ] ] . For example , a [ [ group ( mathematics ) |group ] ] is a set with a [ [ binary operation ] ] , a rule for combining two members of that set to produce a third , which satisfies some of the same basic properties as addition of integers . Other algebraic structures include [ [ ring ( mathematics ) |rings ] ] and [ [ field ( mathematics ) |fields ] ] . [ [ Linear algebra ] ] , which deals with [ [ linear equation ] ] s and [ [ linear mapping ] ] s , is used for modern presentations of [ [ geometry ] ] , < ! -- Berger 's `` Geometry '' must be cited here -- > and has many practical applications ( in [ [ weather forecasting ] ] , for example ) . There are many areas of mathematics that belong to algebra , some having `` algebra '' in their name , such as [ [ commutative algebra ] ] , and some not , such as [ [ Galois theory ] ] .

The word `` algebra '' is not only used for naming an area of mathematics and some subareas ; it is also used for naming some sorts of algebraic structures , such as an [ [ algebra over a field ] ] , commonly called an `` algebra '' . Sometimes , the same phrase is used for a subarea and its main algebraic structures . For example , the subject known as [ [ Boolean algebra ] ] studies [ [ Boolean algebra ( structure ) |structures called Boolean algebras ] ] . A mathematician specialized in algebra is called an algebraist .

== Etymology ==
[ [ File : Muḥammad ibn Mūsā al-Khwārizmī.png|thumb|upright=0.8|The word `` algebra '' comes from the title of a book by [ [ Muhammad ibn Musa al-Khwarizmi ] ] . < ref > Esposito , John L. ( 2000 ) . ''The Oxford History of Islam '' . Oxford University Press . p. 188 . { { ISBN|978-0-19-988041-6 } } . < /ref > ] ]

The word `` algebra '' comes from the { { lang-ar|الجبر|lit=reunion of broken parts , < ref name= '' oed '' / > [ [ bonesetting ] ] < ref name= '' CRC Press '' / > |translit=al-jabr } } from the title of the early 9th century book `` [ [ The Compendious Book on Calculation by Completion and Balancing|ʿIlm al-jabr wa l-muqābala ] ] '' `` The Science of Restoring and Balancing '' by the [ [ Persian people|Persian ] ] mathematician and astronomer [ [ Muḥammad ibn Mūsā al-Khwārizmī|al-Khwarizmi ] ] . In his work , the term `` al-jabr '' referred to the operation of moving a term from one side of an equation to the other , المقابلة `` al-muqābala '' `` balancing '' referred to adding equal terms to both sides . Shortened to just `` algeber '' or `` algebra '' in Latin , the word eventually entered the English language during the 15th century , from either Spanish , Italian , or [ [ Medieval Latin ] ] . It originally referred to the surgical procedure of setting [ [ Broken bone|broken ] ] or [ [ Dislocated|dislocated bones ] ] . The mathematical meaning was first recorded { { in lang|en } } in the 16th century. < ref > { { cite encyclopedia|title=Algebra|editor=T . F. Hoad|encyclopedia=The Concise Oxford Dictionary of English Etymology|publisher=Oxford University Press|location=Oxford|year=2003|url=https : //archive.org/details/conciseoxforddic00tfho|url-access=subscription|doi=10.1093/acref/9780192830982.001.0001|isbn=978-0-19-283098-2 } } < /ref >

== Different meanings of `` algebra '' ==
The word `` algebra '' has several related meanings in mathematics , as a single word or with qualifiers .
* As a single word without an [ [ Article_ ( grammar ) |article ] ] , `` algebra '' names a broad part of mathematics .
* As a single word with an article or in the plural , `` an algebra '' or `` algebras '' denotes a specific mathematical structure , whose precise definition depends on the context . Usually , the structure has an addition , multiplication , and scalar multiplication ( see [ [ Algebra over a field ] ] ) . When some authors use the term `` algebra '' , they make a subset of the following additional assumptions : [ [ Associative property|associative ] ] , [ [ Commutative property|commutative ] ] , [ [ Unital algebra|unital ] ] , and/or finite-dimensional . In [ [ universal algebra ] ] , the word `` algebra '' refers to a generalization of the above concept , which allows for [ [ Operation ( mathematics ) |n-ary operations ] ] .
* With a qualifier , there is the same distinction :
** Without an article , it means a part of algebra , such as [ [ linear algebra ] ] , [ [ elementary algebra ] ] ( the symbol-manipulation rules taught in elementary courses of mathematics as part of [ [ primary education|primary ] ] and [ [ secondary education ] ] ) , or [ [ abstract algebra ] ] ( the study of the algebraic structures for themselves ) .
** With an article , it means an instance of some algebraic structure , like a [ [ Lie algebra ] ] , an [ [ associative algebra ] ] , or a [ [ vertex operator algebra ] ] .
** Sometimes both meanings exist for the same qualifier , as in the sentence : `` [ [ Commutative algebra ] ] is the study of [ [ commutative ring ] ] s , which are [ [ algebra ( ring theory ) |commutative algebras ] ] over the integers '' .

== Algebra as a branch of mathematics ==

Algebra began with computations similar to those of [ [ arithmetic ] ] , with letters standing for numbers. < ref name=citeboyer / > This allowed proofs of properties that are true no matter which numbers are involved . For example , in the [ [ quadratic equation ] ]
: $ a x ^2+ b x + c =0, $
$ a , b , c $ can be any numbers whatsoever ( except that $ a $ can not be $ 0 $ ) , and the [ [ quadratic formula ] ] can be used to quickly and easily find the values of the unknown quantity $ x $ which satisfy the equation . That is to say , to find all the solutions of the equation .

Historically , and in current teaching , the study of algebra starts with the solving of equations , such as the quadratic equation above . Then more general questions , such as `` does an equation have a [ [ Solution ( equation ) |solution ] ] ? `` , `` how many [ [ Zero of a function|solutions ] ] does an equation have ? `` , `` what can be said about the nature of the solutions ? '' are considered . These questions led extending algebra to non-numerical objects , such as [ [ permutation ] ] s , [ [ vector ( mathematics ) |vectors ] ] , [ [ matrix ( mathematics ) |matrices ] ] , and [ [ polynomial ] ] s. The structural properties of these non-numerical objects were then formalized into [ [ algebraic structure ] ] s such as [ [ group ( mathematics ) |groups ] ] , [ [ ring ( mathematics ) |rings ] ] , and [ [ field ( mathematics ) |fields ] ] .

Before the 16th century , mathematics was divided into only two subfields , [ [ arithmetic ] ] and [ [ geometry ] ] . Even though some methods , which had been developed much earlier , may be considered nowadays as algebra , the emergence of algebra and , soon thereafter , of [ [ infinitesimal calculus ] ] as subfields of mathematics only dates from the 16th or 17th century . From the second half of the 19th century on , many new fields of mathematics appeared , most of which made use of both arithmetic and geometry , and almost all of which used algebra .

Today , algebra has grown considerably and includes many branches of mathematics , as can be seen in the [ [ Mathematics Subject Classification ] ] < ref > { { cite web|url=https : //www.ams.org/mathscinet/msc/msc2010.html|title=2010 Mathematics Subject Classification|access-date=2014-10-05|archive-date=2014-06-06|archive-url=https : //web.archive.org/web/20140606010248/http : //www.ams.org/mathscinet/msc/msc2010.html|url-status=live } } < /ref > where none of the first level areas ( two digit entries ) are called `` algebra '' . Today algebra includes section 08-General algebraic systems , 12- [ [ Field theory ( mathematics ) |Field theory ] ] and [ [ polynomial ] ] s , 13- [ [ Commutative algebra ] ] , 15- [ [ Linear algebra|Linear ] ] and [ [ multilinear algebra ] ] ; [ [ matrix theory ] ] , 16- [ [ associative algebra|Associative rings and algebras ] ] , 17- [ [ Nonassociative ring ] ] s and [ [ Non-associative algebra|algebras ] ] , 18- [ [ Category theory ] ] ; [ [ homological algebra ] ] , 19- [ [ K-theory ] ] and 20- [ [ Group theory ] ] . Algebra is also used extensively in 11- [ [ Number theory ] ] and 14- [ [ Algebraic geometry ] ] .

== History ==
{ { Main|History of algebra|Abstract algebra # History|Timeline of algebra } }

The use of the word `` algebra '' for denoting a part of mathematics dates probably from the 16th century . { { citation needed|date=July 2022 } } The word is derived from the [ [ Arabic language|Arabic word ] ] `` al-jabr '' that appears in the title of the treatise `` [ [ Al-Kitab al-muhtasar fi hisab al-gabr wa-l-muqabala ] ] '' ( `` The Compendious Book on Calculation by Completion and Balancing '' ) , written in circa 820 by [ [ Al-Kwarizmi ] ] .

''Al-jabr '' referred to a method for transforming [ [ equation ( mathematics ) |equation ] ] s by subtracting [ [ like terms ] ] from both sides , or passing one term from one side to the other , after changing its sign .

Therefore , `` algebra '' referred originally to the manipulation of equations , and , by extension , to the [ [ theory of equations ] ] . This is still what historians of mathematics generally mean by the term `` algebra '' . { { citation needed|date=July 2022 } }

In mathematics , the meaning of `` algebra '' has evolved after the introduction by [ [ François Viète ] ] of symbols ( [ [ variable ( mathematics ) |variable ] ] s ) for denoting unknown or incompletely specified numbers , and the resulting use of the [ [ mathematical notation ] ] for equations and [ [ formula ] ] s. So , algebra became essentially the study of the action of [ [ operation ( mathematics ) |operation ] ] s on [ [ expression ( mathematics ) |expression ] ] s involving variables . This includes but is not limited to the theory of equations .

At the beginning of the 20th century , algebra evolved further by considering operations that act not only on numbers but also on elements of so-called [ [ mathematical structure ] ] s such as [ [ group ( mathematics ) |group ] ] s , [ [ field ( mathematics ) |field ] ] s and [ [ vector space ] ] s. This new algebra was called `` [ [ Moderne Algebra|modern algebra ] ] '' by [ [ van der Waerden ] ] in his eponymous treatise , whose name has been changed to `` Algebra '' in later editions .

=== Early history ===
[ [ File : Image-Al-Kitāb al-muḫtaṣar ḥisāb al-ğabr wa-l-muqābala.jpg|thumb|upright=0.8|A page from [ [ : en : Muhammad ibn Musa al-Khwarizmi|Al-Khwārizmī ] ] 's `` [ [ The Compendious Book on Calculation by Completion and Balancing|al-Kitāb al-muḫtaṣar ḥisāb al-ğabr wa-l-muqābala ] ] '' ] ]

The roots of algebra can be traced back to the ancient [ [ Babylonian mathematics|Babylonians ] ] , < ref > { { cite book |last=Struik |first=Dirk J . |year=1987 |title=A Concise History of Mathematics |location=New York |publisher=Dover Publications |isbn=978-0-486-60255-4 |url-access=registration |url=https : //archive.org/details/concisehistoryof0000stru_m6j1 } } < /ref > who developed an advanced arithmetical system with which they were able to do calculations in an [ [ algorithm ] ] ic fashion . The Babylonians developed formulas to calculate solutions for problems typically solved today by using [ [ linear equation ] ] s , [ [ quadratic equation ] ] s , and [ [ indeterminate equation|indeterminate linear equations ] ] . By contrast , most [ [ Ancient Egyptian mathematics|Egyptians ] ] of this era , as well as [ [ Greek mathematics|Greek ] ] and [ [ Chinese mathematics ] ] in the 1st millennium BC , usually solved such equations by geometric methods , such as those described in the `` [ [ Rhind Mathematical Papyrus ] ] '' , [ [ Euclid 's Elements|Euclid 's `` Elements '' ] ] , and `` [ [ The Nine Chapters on the Mathematical Art ] ] '' . The geometric work of the Greeks , typified in the `` Elements '' , provided the framework for generalizing formulae beyond the solution of particular problems into more general systems of stating and solving equations , although this would not be realized until [ [ Mathematics in medieval Islam|mathematics developed in medieval Islam ] ] . < ref > See { { harvnb|Boyer|1991 } } . < /ref >

By the time of [ [ Plato ] ] , Greek mathematics had undergone a drastic change . The Greeks created a [ [ Greek geometric algebra|geometric algebra ] ] where terms were represented by sides of geometric objects , usually lines , that had letters associated with them. < ref name=citeboyer > See { { harvnb|Boyer|1991 } } , `` Europe in the Middle Ages '' , p. 258 : `` In the arithmetical theorems in Euclid 's `` Elements '' VII–IX , numbers had been represented by line segments to which letters had been attached , and the geometric proofs in al-Khwarizmi 's `` Algebra '' made use of lettered diagrams ; but all coefficients in the equations used in the `` Algebra '' are specific numbers , whether represented by numerals or written out in words . The idea of generality is implied in al-Khwarizmi 's exposition , but he had no scheme for expressing algebraically the general propositions that are so readily available in geometry . `` < /ref > [ [ Diophantus ] ] ( 3rd century AD ) was an [ [ Alexandria ] ] n Greek mathematician and the author of a series of books called `` [ [ Arithmetica ] ] '' . These texts deal with solving [ [ algebraic equation ] ] s , < ref > { { cite book |author-link=Florian Cajori |first=Florian |last=Cajori |year=2010 |url=https : //books.google.com/books ? id=gZ2Us3F7dSwC & pg=PA34 |title=A History of Elementary Mathematics With Hints on Methods of Teaching |page=34 |publisher=Read Books Design |isbn=978-1-4460-2221-4 |access-date=2020-10-15 |archive-date=2021-02-21 |archive-url=https : //web.archive.org/web/20210221075950/https : //books.google.com/books ? id=gZ2Us3F7dSwC & pg=PA34 |url-status=live } } < /ref > and have led , in [ [ number theory ] ] , to the modern notion of [ [ Diophantine equation ] ] .

Earlier traditions discussed above had a direct influence on the [ [ History of Iran|Persian ] ] mathematician [ [ Muhammad ibn Musa al-Khwarizmi|Muḥammad ibn Mūsā al-Khwārizmī ] ] ( { { circa|780 } } –850 ) . He later wrote `` [ [ The Compendious Book on Calculation by Completion and Balancing ] ] '' , which established algebra as a mathematical discipline that is independent of [ [ geometry ] ] and [ [ arithmetic ] ] . < ref > { { Cite book|title=Al Khwarizmi : The Beginnings of Algebra|author=Roshdi Rashed|publisher=Saqi Books|date= 2009|isbn=978-0-86356-430-7 } } < /ref >

The [ [ Hellenistic period|Hellenistic ] ] mathematicians [ [ Hero of Alexandria ] ] and Diophantus < ref > { { cite web|url=http : //library.thinkquest.org/25672/diiophan.htm |title=Diophantus , Father of Algebra |access-date=2014-10-05 |url-status=dead |archive-url=https : //web.archive.org/web/20130727040815/http : //library.thinkquest.org/25672/diiophan.htm |archive-date=2013-07-27 } } < /ref > as well as [ [ Indian mathematics|Indian mathematicians ] ] such as [ [ Brahmagupta ] ] , continued the traditions of Egypt and Babylon , though Diophantus ' `` Arithmetica '' and Brahmagupta 's `` [ [ Brāhmasphuṭasiddhānta ] ] '' are on a higher level. < ref > { { cite web|url=http : //www.algebra.com/algebra/about/history/|title=History of Algebra|access-date=2014-10-05|archive-date=2014-11-11|archive-url=https : //web.archive.org/web/20141111040653/http : //www.algebra.com/algebra/about/history/|url-status=live } } < /ref > { { Better source needed|date=October 2017 } } For example , the first complete arithmetic solution written in words instead of symbols , < ref > { { Cite book |last=Mackenzie |first=Dana |url=https : //www.worldcat.org/oclc/761851013 |title=The universe in zero words : the story of mathematics as told through equations |date=2012 |publisher=Princeton University Press |isbn=978-0-691-15282-0 |location=Princeton , N.J. |pages=61 |oclc=761851013 } } < /ref > including zero and negative solutions , to quadratic equations was described by Brahmagupta in his book `` Brahmasphutasiddhanta , '' published in 628 AD. < ref name= '' Bradley '' > { { Cite book |last=Bradley |first=Michael J . |url=https : //www.worldcat.org/oclc/465077937 |title=The birth of mathematics : ancient times to 1300 |date=2006 |publisher=Chelsea House |isbn=978-0-7910-9723-6 |location=New York |page=86 |oclc=465077937 } } < /ref > Later , Persian and [ [ Arabs|Arab ] ] mathematicians developed algebraic methods to a much higher degree of sophistication . Although Diophantus and the Babylonians used mostly special `` ad hoc '' methods to solve equations , Al-Khwarizmi 's contribution was fundamental . He solved linear and quadratic equations without algebraic symbolism , [ [ negative numbers ] ] or [ [ zero ] ] , thus he had to distinguish several types of equations. < ref name= '' Meri2004 '' > { { cite book|first=Josef W.|last=Meri|title=Medieval Islamic Civilization|url=https : //books.google.com/books ? id=H-k9oc9xsuAC & pg=PA31|access-date=2012-11-25|year=2004|publisher=Psychology Press|isbn=978-0-415-96690-0|page=31|archive-date=2013-06-02|archive-url=https : //web.archive.org/web/20130602195207/http : //books.google.com/books ? id=H-k9oc9xsuAC & pg=PA31|url-status=live } } < /ref >

In the context where algebra is identified with the [ [ theory of equations ] ] , the Greek mathematician Diophantus has traditionally been known as the `` father of algebra '' and in the context where it is identified with rules for manipulating and solving equations , Persian mathematician al-Khwarizmi is regarded as `` the father of algebra '' . < ref > { { Cite book|last=Corona|first=Brezina|title=Al-Khwarizmi : The Inventor Of Algebra|publisher=Rosen Pub Group|date= 2006|isbn=978-1404205130|location=New York , United States } } < /ref > < ref > See { { harvnb|Boyer|1991 } } , page 181 : `` If we think primarily of the matter of notations , Diophantus has good claim to be known as the 'father of algebra ' , but in terms of motivation and concept , the claim is less appropriate . The Arithmetica is not a systematic exposition of the algebraic operations , or of algebraic functions or of the solution of algebraic equations '' . < /ref > < ref > See { { harvnb|Boyer|1991 } } , page 230 : `` The six cases of equations given above exhaust all possibilities for linear and quadratic equations ... In this sense , then , al-Khwarizmi is entitled to be known as 'the father of algebra { { ' '' } } . < /ref > < ref > See { { harvnb|Boyer|1991 } } , page 228 : `` Diophantus sometimes is called the father of algebra , but this title more appropriately belongs to al-Khowarizmi '' . < /ref > < ref name= '' Gandz '' > See { { harvnb|Gandz|1936 } } , pp . 263–277 : `` In a sense , al-Khwarizmi is more entitled to be called `` the father of algebra '' than Diophantus because al-Khwarizmi is the first to teach algebra in an elementary form and for its own sake , Diophantus is primarily concerned with the theory of numbers '' . < /ref > < ref > { { Cite journal |last=Christianidis |first=Jean |date=August 2007 |title=The way of Diophantus : Some clarifications on Diophantus ' method of solution|journal= [ [ Historia Mathematica ] ] |volume=34|issue=3|pages=289–305|quote=It is true that if one starts from a conception of algebra that emphasizes the solution of equations , as was generally the case with the Arab mathematicians from al-Khwārizmī onward as well as with the Italian algebraists of the Renaissance , then the work of Diophantus appears indeed very different from the works of those algebraists|doi=10.1016/j.hm.2006.10.003|doi-access= } } < /ref > < ref > { { cite journal |first=G . C. |last= Cifoletti |title= La question de l'algèbre : Mathématiques et rhétorique des homes de droit dans la France du 16e siècle |journal= Annales de l'École des Hautes Études en Sciences Sociales , 50 ( 6 ) |year= 1995 |pages= 1385–1416 |quote= Le travail des Arabes et de leurs successeurs a privilégié la solution des problèmes.Arithmetica de Diophantine ont privilégié la théorie des equations } } < /ref > It is open to debate whether Diophantus or al-Khwarizmi is more entitled to be known , in the general sense , as `` the father of algebra '' . Those who support Diophantus point to the fact that the algebra found in `` Al-Jabr '' is slightly more elementary than the algebra found in `` Arithmetica '' and that `` Arithmetica '' is syncopated while `` Al-Jabr '' is fully rhetorical. < ref > See { { harvnb|Boyer|1991 } } , page 228. < /ref > Those who support Al-Khwarizmi point to the fact that he introduced the methods of `` [ [ Reduction ( mathematics ) |reduction ] ] '' and `` balancing '' ( the transposition of subtracted terms to the other side of an equation , that is , the cancellation of [ [ like terms ] ] on opposite sides of the equation ) which the term `` al-jabr '' originally referred to , < ref name=Boyer-229 > See { { harvnb|Boyer|1991 } } , `` The Arabic Hegemony '' , p. 229 : `` It is not certain just what the terms `` al-jabr '' and `` muqabalah '' mean , but the usual interpretation is similar to that implied in the translation above . The word `` al-jabr '' presumably meant something like `` restoration '' or `` completion '' and seems to refer to the transposition of subtracted terms to the other side of an equation ; the word `` muqabalah '' is said to refer to `` reduction '' or `` balancing '' that is , the cancellation of like terms on opposite sides of the equation '' . < /ref > and that he gave an exhaustive explanation of solving quadratic equations , < ref > See { { harvnb|Boyer|1991 } } , `` The Arabic Hegemony '' , p. 230 : `` The six cases of equations given above exhaust all possibilities for linear and quadratic equations having positive root . So systematic and exhaustive was al-Khwarizmi 's exposition that his readers must have had little difficulty in mastering the solutions '' . < /ref > supported by geometric proofs while treating algebra as an independent discipline in its own right. < ref name= '' Gandz '' / > His algebra was also no longer concerned `` with a series of problems to be resolved , but an [ [ Expository writing|exposition ] ] which starts with primitive terms in which the combinations must give all possible prototypes for equations , which henceforward explicitly constitute the true object of study '' . He also studied an equation for its own sake and `` in a generic manner , insofar as it does not simply emerge in the course of solving a problem , but is specifically called on to define an infinite class of problems '' . < ref name=Rashed-Armstrong > { { Cite book |last1= Rashed |first1= R. |last2= Armstrong |first2= Angela |year= 1994