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x^2-2x-1=0
求:x^4+x^3-5x^2-7x+5的值
人气:391 ℃ 时间:2020-02-05 22:39:59
解答
X^2-2X-1=0
X^4+X^3-5X^2-7X+5
=X^2(X^2-2X-1)+3X^3-4X^2-7X+5
=3X^3-4X^2-7X+5
=3X(X^2-2X-1)+2X^2-4X+5
=-2X^2-4X+5
=2(X^2-2X-1)+7
=7
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