已知x²-4x-1=0,求(1)x²+x²分之1的值(2)x的4次方+x的4次方分之1的值.
人气:308 ℃ 时间:2019-10-19 22:14:07
解答
(1)
x²-4x-1=0
x²-1=4x
x-1/x=4
平方,得
x²-2+1/x²=16
所以
x²+1/x²=16+2=18
(2) 再平方,得
x^4+2+1/x^4 =324
所以
原式=324-2=322
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