Question

What is the sum of 4 - 7i and the conjugate of 2 + 3i ?

A.6 - 4i
B.8 - 21i
C.8 - 4i
D.6 - 10i

Answer 1

The conjugate of a complex number z = a + b i is z * = a - b i. So

(4 - 7i ) + (2 + 3i )* = (4 - 7i ) + (2 - 3i )

… = (4 + 2) + (-7i - 3i)

… = 6 - 10i

and the answer is D.