D
Step-by-step explanation:
(f×g)(x)=-5x(8x^2-5x-9)=-5x(8x^2)-5x(-5x)-5x (-9)=-40x^3+25x^2+45x
x = ± 6i
step-by-step explanation:
x^2 = -36
take the square root of each side
sqrt(x^2) = sqrt(-36)
we know sqrt(ab) = sqrt(a) sqrt(b)
x = ±sqrt(36) sqrt(-1)
we know that sqrt (-1) = i