SOLUTION: Given f(x)=3x^2+x-1 and g(x)=4x+5, find (gf)(x). A. 3x^2+5x+4 B. 12x^3+4x^2-4x C. 12x^3+19x^2+x-5 D. 12x^3+19x^2+9x-5 Thank you

Algebra ->  Functions -> SOLUTION: Given f(x)=3x^2+x-1 and g(x)=4x+5, find (gf)(x). A. 3x^2+5x+4 B. 12x^3+4x^2-4x C. 12x^3+19x^2+x-5 D. 12x^3+19x^2+9x-5 Thank you      Log On


   

Question 996210: Given f(x)=3x^2+x-1 and g(x)=4x+5, find (gf)(x).
A. 3x^2+5x+4
B. 12x^3+4x^2-4x
C. 12x^3+19x^2+x-5
D. 12x^3+19x^2+9x-5
Thank you
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

if +f%28x%29=3x%5E2%2Bx-1 and g%28x%29=4x%2B5,then
%28gf%29%28x%29=%283x%5E2%2Bx-1%29%284x%2B5%29
%28gf%29%28x%29=3x%5E2%2A4x%2Bx%2A4x-1%2A4x%2B5%2A3x%5E2%2B5x-5
%28gf%29%28x%29=12x%5E3%2B4x%5E2-4x%2B15x%5E2%2B5x-5
%28gf%29%28x%29=12x%5E3%2B19x%5E2%2Bx-5
so your answer is: C. 12x%5E3%2B19x%5E2%2Bx-5