Evaluate the expression (4 + 7i)(11 - 4i)and write the result in the form a + bi
A) 61 + 72i
B) 44 + 77i
C) 72 + 61i
D) - 61 - 72i
E) none of these

Question

Quizplus · Accepted Answer

To multiply complex numbers, we use FOIL (First, Outer, Inner, Last) method.
(4 + 7i)(11 - 4i) = 4(11) + 4(-4i) + 7i(11) + 7i(-4i)
= 44 - 16i + 77i - 28i^2 (Remember that i^2 = -1)
= 44 + 61i - 28(-1)
= 44 + 61i + 28
= 72 + 61i
Therefore, the answer is choice C.

Evaluate the Expression (4 + 7i)(11 - 4i)and Write the Result