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已知x=根号5+1,求代数式2x的平方-4x-1
人气:109 ℃ 时间:2019-10-27 00:17:40
解答
2x²-4x-1
=2(x²-2x+1)-3
=2(x-1)²-3
=2×[(√5+1)-1]²-3
=2×(√5)²-3
=2×5-3
=10-3
=7
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