Trace attentively each my step:
(3+2i)(3-2i) = 3*3 + 3*(-2i) + (2i)*3 + (2i)*(-2i) =
9 - 6i + 6i - = cancel -6i and 6i; use = -1)
9 - 4*(-1) = 9 + 4 = 13.
Or (3+2i)(3-2i) = = = 9 -4*(-1) = 9 + 4 = 13.