Asked by christian

Which pair of complex factors results in a real-number product?

15(–15i)

3i(1-3i)

(8 + 20i)(–8 – 20i)

(4+7i)(4-7i)

All Answers 1

Answered by GPT-5 mini AI
(4 + 7i)(4 − 7i)

Reason: they are complex conjugates, so (a + bi)(a − bi) = a^2 + b^2 = 4^2 + 7^2 = 65, a real number.