Answer :
(-21 + 63i + 15i - 45i^2) - (25 + 60i + 36i^2) =
(-21 + 78i + 45) - (-11 + 60i) =
24 + 78i - 60i + 11 =
35 + 18i
(-21 + 78i + 45) - (-11 + 60i) =
24 + 78i - 60i + 11 =
35 + 18i