If f(x) = 2x - 10 ; g (x) = 4x + 20 what is the value of (f + g) (3) ?

1 Answer
Oct 29, 2015

(f+g)(3) = 28

Explanation:

First method:

Add f(x) + g(x)

(2x-10)+(4x+20)

Combine like terms.

=6x+10

Then substitute 3 for x.

=6(3)+10
=18+10
=28

Second method:

Substitute 3 into both functions individually.

f(3)= 2(3)-10
=6-10
=-4

g(3) = 4(3)+20
=12+20
=32

Then add the answers you get from substituting together.

=-4+32
=28