Finding (fg) and simplifying the answers

Question

Let f(x) = x² + 9x and g(x) = 8 - x

Find [f⁄g] (x) and [f⁄g] (4)

Answer 1

f(x) = x^2 +9

f(4) = 16+9 =25

g(x) = 8-x

g(4) = 8-4 = 4

(f/g)(4) =f(4)/g(4) = 25/4

(fg)(4) = f(4)g(4) = 25(4) = 100

or

(f/g)(x) = f(x)/g(x) = (x^2+9)/(8-x)

(f/g)(4) = (4^2+9)/(8-4) = 25/4

(fg)(x) = (x^2+9)(8-x) = -x^3+8x^2-9x+72

(fg)(4) =-4^3+8(4^2) -9(4)+72

= -64+128-36+72

=100