how to do these calculus questions?

Question

I have found the answer for 8 a) which is 18x^2-36x

8b) and c) i am not sure how to do 

Answer 1

y = 2x²(3x – 9)

y = 8x³ – 18x²

y' = 24x² – 36x

y = (3x – 6) / (x(x+6))

y = (3x – 6) / (x² + 6x)

quotient rule(f/g)' = (f'g–fg')/g²

f = (3x – 6)    f' = 3

g = (x² + 6x)    g' = 2x + 6

y' = [3(x² + 6x) – (3x – 6)(2x + 6) ] / (x² + 6x)²

can be simplified a bit

y' = [3x² + 18x – (6x² – 12x + 18x – 36) ] / (x² + 6x)²

y' = [3x² + 18x – 6x² + 12x – 18x + 36 ] / (x² + 6x)²

y' = (–3x² + 12x + 36) / (x⁴ + 12x³ + 36x²)