If (a + bi)(a - bi) = 73 and a + b = 12 then a² + b² equals?
- 73
- 74
- 75
- None of these
Explanation
(a + bi)(a - bi) = a² - (bi)² = a² - b²i² = a² - b²(-1) = a² + b²
So (a + bi)(a - bi) = a² + b² = 73
Last verified on 25-05-2026
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