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If a + 1/a = 5, then a^2 + 1/a^2 is
A25
B27
C21
D23
Answer & Solution
Correct answer: D. 23
(a + 1/a)^2 = a^2 + 2 + 1/a^2 = 25. So a^2 + 1/a^2 = 25 - 2 = 23.
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