What is (5+2i) * (5+2i) ?

(5+2i) * (5+2i)

Distribute ...

25 + 10 i + 10 i + 4i^2

Remember ... when there is a number with i^2 it will equal to (-1) ...

So that means in this question ... I replace 4i^2 with - 4 because 4 (-1) = - 4

Now I can combine like terms ...

25 + 10i + 10i - 4

Soo ... The answer is 21 + 20i

25+10i+10i+4i^2

25-4

21+20i

20i+21