Glossary for College Algebra Lesson 4: Equations

Identity

An identity is an equation that is true regardless of what values are substituted in for its variables.
Examples:

x+1=x-3+4
(y-2)(y+2)=y^2-4

Conditional Equation

A conditional equation is an equation that is true only for certain values of its variables.
Examples:

y+3=5
2x^2-9x-25=10

Isolating a Variable

Isolating a variable means rearranging and modifying an equation, according to the rules of algebra, so that a variable is all by itself on one side of the equation.  If we started off with the equation x-3=6, we could add 3 to both sides of the equation to end up with x=9.  The variable x is now isolated.