Algebra (from the Arabic "al-jabr" meaning "reunion", "connection" or "completion") is a branch of mathematics which may be roughly characterized as a generalization and extension of arithmetic; it also refers to a particular kind of abstract algebra structure, the algebra over a field.

Algebra may be roughly divided into the following categories:

• elementary algebra, where the properties of operations on the real number system are recorded, symbols are used as "place holders" to denote constants and variables, and the rules governing mathematical expressions and equations involving these symbols are studied,
• abstract algebra, where algebraic structures such as groups, rings and as fields are axiomatically defined and investigated.
• The specific properties of vector spaces are studied in linear algebra.
• universal algebra, where those properties common to all algebraic structures are studied.
• computer algebra, where algorithms for the symbolic manipulation of mathematical objects are collected

In advanced studies axiomatic algebraic systems like groups, rings, fields, and algebras over a field are investigated in the presence of a natural topology compatible with algebraic structure. The list includes

• Normed linear spaces
• Banach spaces
• Hilbert spaces
• Banach algebras
• Normed algebras
• Topological algebras
• Topological groups

Contents

1 Forms of algebra 1.1 Linear equations 1.2 Quadratic equations 1.3 Cubic equations 1.4 Exponential equations 2 Factoring trinomials 2.1 Simple factoring 2.2 Two variables 2.3 Symbols 3 Symbolic method 4 See also 5 External links

Forms of algebra

There are many forms of algebraic equations. Some are listed below:

• Linear equations
• Quadratic equations
• Cubic equations
• Exponential equations

Linear equations

Linear equations are written in the form y = Mx + B.

• y is the answer to the equation.
• M is the co-efficient of the variable, and it represents the slope. The slope is the steepness of the line produced when the equation is graphed
• x is the variable in the equation. The variable is the part that can be changed. When x changes, so does y. When the equation is graphed, the line showes what y is for each value of x.
• B is the number added to the equation. In the expression 2x + 3, B = 3. B also represents the y intercept on a graph.

The y intercept is where the line crosses the y axis.

Quadratic equations

Quadratic equations are written in the form y = ax² + bx + c. When a quadratic equation is graphed, it produces a curved line called a parabola.

• a is the co-efficient of the variable squared
• b is the co-efficient of the variable
• c is the extra added number. It is the same as the B in Linear equations

Cubic equations

Cubic equations are written in the form y = ax³ + bx² + cx + d. In this form, there are three x-intercepts. When graphed, the line will start going up, then curve to go down, then switch again to go up. (the opposite can occur with negative variables)

• a is the co-efficient of the variable cubed
• b is the co-efficient of the variable squared
• c is the co-efficient of the variable
• d is the non-variable

Exponential equations

Exponential equations are written in the form y = m^x + b.

Factoring trinomials

Simple factoring

Trinomials are algebraic expressions consisting of three unlike terms, such as x^{2 + 3x + 2. They can be factored using the "FOIL" technique. You factor the expression by using two sets of perenthesis, each consisting of two terms, where the first, outside, inside, and last numbers of both sets multiplied together and added equal the trinomial. E.g.,}

^{x2 + 5x + 6}

is equivalent to

(x + 3)(x + 2)

Firsts (x times x) + Outsides (x times 2) + Insides (3 times x) + Lasts (3 times 2) = The trinomial (x^{2 + 5x + 6).}

^{The last numbers in each set of parenthesis have another relationship. When multiplied together, they always equal the last number (3 times 2 equals 6), and when added, they equal the co-efficient of the variable (3 plus 2 equals 5). The co-efficient is the number in front of the variable that you multiply it by. This is because they're both multiplied by the variable, and then added.}

^{Two variables}

^{Sometimes, you get expressions such as: 3x2 + 8xy + 4y2. In this situation, the factored form will look like: (3x + 2y)(x + 2y). 3x times x is 3x2, 3x times 2y is 6xy, 2y times x is 2xy, and 2y times 2y is 4y2. This time, the co-efficients of x have to be multiplied with the co-efficient of x2, and same with x.}

^Symbols

^{Depending on whether the numbers are added or subtracted, you may need to use different symbols in the parenthesis.}

• ^{If you add the mx and add the b, the symbols are both plus.}
• ^{If you add the mx and subtract the b, the symbols are one plus and one minus.}
• ^{If you subtract the mx and add the b, the symbols are both minus}
• ^{If you subtract the mx and subtract the b, the symbols are one plus and one minus.}

^{Symbolic method}

^{The symbolic method is a way to figure out a variable when it's on both sides of the equation. E.g.,}

^{3x + 25 = 5x + 5}

• ^{The first step is to isolate the variable. By subtracting 3x from both sides, you get 25 = 2x + 5.}

• ^{The second step is to get only the variable on one side. To do this, you subtract 5 from both sides to get 20 = 2x.}

• ^{The last step is to get just 1 x. Divide both sides by the co-efficient, in this case 2, and you have 10 = x.}

^{The word algebra is also used for various algebraic structures:}

• ^{algebra over a field}
• ^{algebra over a set}
• ^{Boolean algebra}
• ^{sigma-algebra}

^{See also}

• ^{Diophantus, "father of algebra"}
• ^{Mohammed al-Khwarizmi}

^{External links}

Our sister project, Wikibooks, provides an electronic book on Algebra.

• ^{Algebra Lessons of Life http://kagawasan.netfirms.com/english/ilearnedmorethanjustalgebra.shtml}
• ^{Curriculum and Assessment in an Age of Computer Algebra Systems http://www.ericdigests.org/2003-1/age.htm}