Question

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

Answer 1

Answer: x^3 + 8x^2 +11x - 20

Proof of validity is shown below.

Answer 2

f(x) • g(x)
SImply multiply the functions,
(x2+3x−4)(x+5)
Distribute then simplify.
x(x2+3x−4) + 5(x2+3x−4)
Further distribute x and 5, respectively, to terms inside parentheses, and combine like terms.
x3 + 3x2 -4 + 5x2 + 15x -20
Simplify for the last time.
The final and simplified expression or answer is: x3 + 8x2 + 11x - 20
f(x) • g(x) = x3 + 8x2 + 11x - 20