Question

Let f(x) = x2 + 3x – 4 and g(x) = x + 5. Find f(x) • g(x).

Answer 1

f(x) times g(x) simply means:
\[(x ^{2}+3x-4)(x+5)\]

When we FOIL, we get:
\[x ^{3}+3x ^{2}-4x+5x ^{2}+15x ^{2}-20\]

It's easier to combine like terms when they're ordered together, so
\[x ^{3}+15x ^{2}+3x ^{2}+5x ^{2}-4x-20\]

Then we combine like terms for your answer
\[x ^{3}+23x ^{2}-4x-20\]