alleryWhen x + 1/x equals 3, compute the fourth power sum x^4 + 1/x^4.
A49
B51
C45
D47
Answer & Solution
Correct answer: D. 47
Squaring twice gives x^2 + 1/x^2 = 7, and then (x^2 + 1/x^2)^2 - 2 = 49 - 2 = 47.
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