Question

Which of the following expressions represents the product below? (4i + 3)(5 - 2i)

Answer 1

(4i+3)(5-2i)
=20i-8i^2+15-6i
=14i+23

Answer 2

Here you have two complex numbers. Multiplying these numbers remember that

`i^2=-1.`

Now

`(4i + 3)(5 - 2i)=4i\cdot 5-4i\cdot 2i+3\cdot 5-3\cdot 2i=20i-8i^2+15-6i=\\ \\20i-8\cdot (-1)+15-6i=20i+8+15-6i=(8+15)+(20i-6i)=23+14i.`

Answer: 23+14i.