(2 + 3i)^2 = 4 + 12i + 9(-1)
= 4 + 12i - 9
= -5 + 12i
(2 - 3i)^2 = 4 - 12i - 9(-1)
= 4 - 12i + 9
= 13 - 12i
REsult
= -5 + 12i + 13 - 12i
= 8 - 0i
Then
a = 8 and b = 0
