r^3+216/r+6=

Answer 1

r ^ 3 + 216 / r + 6 = r ^ 3 * r / r + 216 / r + 6 r / r =

( r ^ 4 + 216 + 6 r )/ r=

( r ^ 4 + 6 r + 216 ) / r

Answer 2

I am very sure you meant:
(r^3+216)/(r+6)

= (r+6)(r^2 - 6r + 36)/(r+6)

= r^2 - 6r + 36