Question

Which pair of complex factors results in a real number product? 15(–15i) 3i(1 – 3i) (8 + 20i)(–8 – 20i) (4 + 7i)(4 – 7i)

Answer 1

D. (4+7i)(4-7i)

Explanation:

Answer 2

(4 + 7i)(4 – 7i)

Explanation:

This pair will produce a real answer because they are complex conjugates.

Complex conjugates ( a+bi) (a-bi) when multiplied together form a real number ( a^2 + b^2)