Question

For f(x)=4x+1 and g(x)=x^2-5 find (fg)(x)

Answer 1

4x^3+x^2-20x-5

Explanation:

f(x)=4x+1 and g(x)=x^2-5

(fg)(x) = f(x) *g(x)

= (4x+1) *(x^2-5)

FOILing

First 4x*x^2 = 4x^3

outer 4x*-5 = -20x

inner 1 * x^2 = x^2

last 1 * -5 = -5

Add them together

= 4x^3 -20x+x^2-5

Put the terms in order from greatest power to least power

=4x^3+x^2-20x-5