Question

Which of the following products yield a real number? Select all that apply.

Answer 1

Answer:

The choice 4 and 6 ;

$7i(7i)$

and

$(9 + 3i)(9 - 3i)$

Step-by-step explanation:

$7i(7i) = 49 {i}^{2} = - 49$

__o_o__

$(9 + 3i)(9 - 3i) \\ = 81 - 27i + 27i - 9 {i}^{2} \\ = 81 + 9 \\ = 90$