Multiply. Write your answer in a +bi form.
-$(3+9 \mathrm{i})(2+7 \mathrm{i})$
A) $69-3 \mathrm{i}$
B) $-57+39 i$
C) -57 - $39 i$
D) $63 i^{2}+39 i+6$

Question

Quizplus · Accepted Answer

To multiply two complex numbers, you apply the distributive property (FOIL method) to combine them. For $(3+9i)(2+7i)$, you get: $3*2 + 3*7i + 9i*2 + 9i*7i$. Simplifying this, you get $6 + 21i + 18i + 63i^2$. Since $i^2 = -1$, this simplifies further to $6 + 39i - 63$, which equals $-57 + 39i$.

Multiply Write Your Answer in a +Bi Form (3+9i)(2+7i)(3+9 \mathrm{i})(2+7 \mathrm{i})(3+9i)(2+7i)

Multiply Write Your Answer in a +Bi Form $(3+9 \mathrm{i})(2+7 \mathrm{i})$