Answer:
-20 + 46i
Step-by-step explanation:
(3 + 5i) (5 + 7i)
= (3 × 5 - 5 × 7) + (3 × 7 + 5 × 5) i
= (-20) + (46) i
= -20 + 46i
[tex](3 + 5i)(5 + 7i) \in \: \C \\ = 15 + 21i + 25i - 35 \\ = - 20 + 46i \\ = 2( - 10 + 23i)[/tex]