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不等式X的4次方减2X的平方大于X的平方减1的答案
人气:385 ℃ 时间:2019-08-20 09:41:30
解答
x^4-2x^2>x^2-1
x^4-3x^2+1>0
(x^2-3/2)^2>5/4
x^2-3/2>√5/2或x^2-3/2<-√5/2
x^2>(3+√5)/2或x^2<(3-√5)/2
(3+√5)/2=[(1+√5)/2]^2
(3-√5)/2=[(1-√5)/2]^2
x^2>[(1+√5)/2]^2,x>(1+√5)/2或x<-(1+√5)/2
x^2<[(1-√5)/2]^2,-(√5-1)/2
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