If x^2+(1/x^2)=5, x^4+(1/x^4)=?	Select the correct option.
A) 23 B) 11 C) 12 D) 14 E) 15
-&gt; x^4+(1/x^4)=(x^2)^2+(1/x^2)^2=(x^2+1/x^2)^2-2x^2(1/x^2)=5^2-2=23.   Thus, the answer is 23.
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If x^2+(1/x^2)=5, x^4+(1/x^4)=?