# Equation

A mathematical equation is a formula containing an equals sign ( = ) with a mathematical expression on each side of it. The equals sign says that both sides are exactly the same.

There are two kinds of mathematical equations:

• The kind of equation that is either true or false; these are also called identities
Example: $2 \cdot (x+4)=2x+8 \rightarrow true$
• The kind of equation that lets you calculate the value of one or several variables. The equation is only true if the variable(s) have that value.
Example: $2 \cdot x=8 \rightarrow x=4$

The second kind is often used to solve problems in which you have to know the value of some variables. For example, if 2x = 8, x = 8 / 2 = 4.

The second kind of equation is used in algebra. For example, to solve the equation 2x = 8 by finding x you would follow an algebraic rule. Then you can work out that x = 4.

## Types of equations

Equations can be classified by the types of operations and quantities involved. Some types of equations are: