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If x + iy = (a + ib)/(a - ib), then x² + y² equals:

A(a² + b²)/(a² - b²)
Ba² + b²
C1
D0
Answer & Solution
Correct answer: C. 1
**Take modulus on both sides:** |x + iy| = |a + ib|/|a - ib|. But |a + ib| = |a - ib| = √(a² + b²), so |x + iy| = 1, i.e., √(x² + y²) = 1 → x² + y² = 1.
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