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If x^2+(1/x^2)=4, x^4+(1/x^4)=? A. 10 B. 11 C. 12 D. 14

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If x^2+(1/x^2)=4, x^4+(1/x^4)=? A. 10 B. 11 C. 12 D. 14

by Max@Math Revolution » Thu Mar 17, 2016 5:26 pm
If x^2+(1/x^2)=4, x^4+(1/x^4)=?

A. 10
B. 11
C. 12
D. 14
E. 15


* A solution will be posted in two days.
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by Max@Math Revolution » Mon Mar 21, 2016 3:26 am
If x^2+(1/x^2)=4, x^4+(1/x^4)=?

A. 10
B. 11
C. 12
D. 14
E. 15


-> x^4+(1/x^4)=(x^2)^2+(1/x^2)^2=(x^2+1/x^2)^2-2x^2(1/x^2)=4^2-2=14.
Thus, the answer is D.
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