If x^4 + x^(-4) = 7, what is the value of x^8 + x^(-8) =?

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by BTGmoderatorDC » Sat Oct 16, 2021 5:55 pm

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If x^4 + x^(-4) = 7, what is the value of x^8 + x^(-8) =?

A. 14
B. 21
C. 47
D. 49
E. 51

OA C

Source; Magoosh

Source: Beat The GMAT — Problem Solving | Sat Oct 16, 2021 5:55 pm

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