What is $z \cdot \bar{z}$ when $z = a + ib$?
A$a^{2} + b^{2}$
B$a^{2} - b^{2}$
C$a + b$
D$ab$
Answer & Solution
Correct answer: A. $a^{2} + b^{2}$
$(a + ib)(a - ib) = a^{2} - i^{2}b^{2} = a^{2} + b^{2}$. This is $|z|^{2}$.
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