perform indicated operation then express in lowest terms?

Question

[r^3t/t +1] + [r^3/t+1]

Answer 1

the indicated operation is addition... you can add the given ratios since the denominator is common.

once we add, we get

(r^3*t + r^3)/(t+1)

from the numerator, we can factor out r^3...

[r^3(t+1)]/(t+1)

t+1 cancels out and remaining term is..

r^3

Answer 2

taking LCDas t+1
=r^(t+1)/(t+1)
=r^3