Variable
Letter used as a substitute for an unknown value, or number. In the equation y = 3x + 2, both y and x are variables.
Constant
A number that doesn’t change, in an equation or expression. We may not know its value, but it’s "constant" in contrast to a variable, which varies. In the equation y = 3x + 2, 3 and 2 are constants. In the equation y = mx + b, m and b are constants (just unknown).
Variable Expression
A combination of numbers and mathematical symbols that does not contain an equals sign. xy is a variable expression, as is x + 3.
Equation
A combination of mathematical expressions and symbols that contains an equals sign. 3 + 7 = 10 is an equation, as is x + y = 3.
Linear Equation
An equation that does not contain exponents or multiple variables multiplied together. x + y = 3 is a linear equation; xy = 3 and y = x^2 are not. When plotted on a coordinate plane, linear equations create lines.
Simultaneous Equations
Two or more distinct equations containing two or more variables.
System of Equations
See simultaneous equations (above).
Factored Form
Presenting an expression as a product. In factored form, expressions are multiplied together. The expression (x + 1)(x – 1) is in factored form: (x + 1) and (x – 1) are the factors. In contrast, x^2 - 1 is not in factored form; it is in distributed form.
Distributed Form
Presenting an expression as a sum or difference. In distributed form, terms are added or subtracted. x^2 – 1 is in distributed form, as is x^2 + 2x + 1. In contrast, (x + 1)(x – 1) is not in distributed form; it is in factored form.
