Question

Multiply and express the answer in a+bi form : (8-4i)(6+i)

Answer 1

Multiply the complex numbers:

(8 – 4i) · (6 + i)

= (8 – 4i) · 6 + (8 – 4i) · i

= 8 · 6 – 4i · 6 + 8 · i – 4i · i

= 48 – 24i + 8i – 4i²          (but, i² = – 1)

= 48 – 24i + 8i – 4 · (– 1)

= 48 – 24i + 8i + 4

= 48 + 4 – 24i + 8i

= 52 – 16i    <————    this is the answer.


I hope this helps. =)