Question

Compute (1+ 2i)(1 − 2i).

Answer 1

5

Explanation:

This is an example of conjugate binomials. So we are going to solve it like we would do for a regular conjugate binomial. Just remember that i² = -1

So we have:

`(1+2i)(1-2i)= (1-4i^2)= (1-4(-1))= 1 +4 = 5`

Therefore, (1+ 2i)(1 − 2i) = 5