Question

r^3-t^3/r^2-t^2

Answer 1

r^3 -t^3 = (r-t) (r^2 +rt +t^2)
r^2 -t^2 =(r-t) (r^2 +rt +t^2)
r^3-t^3/r^2-t^2 = [(r-t) (r^2 +rt +t^2)]/ [(r-t) (r^2 +rt +t^2)]
Cancel (r-t)

r^3-t^3/r^2-t^2 = ( r^2 +rt +t^2) / (r +t)