Multivariable Expressions:

Example:

    a)   5y – 2z when y = 3 and z = -1

             5(3) – 2(-1) (two negative = positive)

            15 + 2 = 17

    (b)    3a + 4b – 4a +3b when a = 5 and b = 6

            3(5) + -4(5) = 

            15 – 20 = -5

            4(6) + 3(6) =

            24 + 18 = 42

            -5 + 42 = 37 (bigger number is positive, so it stay’s positive)

Example:

    3(s+2t) - 6t + 4s if s = -2 and t = 32

First,

    use the distributive law to fin 3(s + 2t).

    Multiply 3 by s and multiply 2 by 2t:

    3(s) + 3(2t) = 3s + 6t

The expression now is:

        3s + 6t - 6t + 4s

Combine the two s terms and the two t terms:

       3(-2) + 4(-2) = 7s

        6t – 6t = 0

The expression is now just 7s.

        7(-2) = -14

Answer: -14