Calculus-finding derivatives?

Question

I am having a little trouble differentiating this so any help would be greatly appreciated!
f(r)=r^(3/4)(r^3-r^2)

Answer 1

f(r)=r^(3/4)(r^3-r^2)

= {r^(3/4)(r^3) - r^(3/4)(r^2)}

Formula : aⁿ * a^m = a^n+m

= {( r^(3/4)+3) -( r^(3/4)+2)}

f(r)= {r^(15/4) - r^(11/4)}

Apply derivative each side.

d/dr(f(r) )= d/dr {r^(15/4) - r^(11/4)}

f'(r) = {d/dr r^(15/4)} - {d/dr r^(11/4)}

Apply power rule of derivative : d/dx xⁿ = nx^n-1

= {15/4 r^(15/4)-1} -{11/4r^(11/4)-1}

= {(15/4) r^(11/4) - (11/4) r^(7/4)}

f'(r) = 1/4{ 15 r^(11/4) - 11 r^(7/4)}