Question

How do you solve this?

(5+i)(5+2i)

Answer 1

23 +15i

Explanation:

Multiply the binomials in the usual way, then replace i² by -1 and simplify.

(5 +i)(5 +2i) = (5)(5) +(5)(2i) +(i)(5) +(i)(2i) = 25 +10i +5i +2i²

= 25 +15i +2(-1)

= 23 +15i