複數(三)乘法

例子:

(3 + 2i) x (4 + 5i) = 3 x (4 + 5i) + 2i x (4 + 5i)

= 12 + 15i + 8i + 10(i x i)

= 12 + 23i + 10 x (-1)

= 12 + 23i – 10

= 2 + 23i