A coefficient is a number that is multiplied by a variable.

• In the expression , the coefficient of  is 3.
• In the expression , the coefficient of  is 1, because .

In an expression like , the number 2 is called the constant term. It doesn’t change when the variable changes.

• In the expression , the constant term is 9.
• In the expression , the constant term is -8.
• In the expression , the constant term is 12.

A system of equations is a set of 2 or more equations. Each equation has 2 or more variables. A solution to the system is values for the variables that make all the equations true.

These equations make up a system of equations:

The solution to this system is and . When these values are substituted for and , both equations are true: and .

Terms are the parts of an expression that are added together. They can be a single number, a variable, or a number and a variable that are multiplied together.

• 7, , and  are examples of terms.
• The expression has 3 terms: , 3, and -18.