已知y²+3y-1=0,求y^4/(y^8-3y^4+1)的值.
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已知y²+3y-1=0,求y^4/(y^8-3y^4+1)的值.
已知y²+3y-1=0,求y^4/(y^8-3y^4+1)的值.
已知y²+3y-1=0,求y^4/(y^8-3y^4+1)的值.
y^4/(y8-3y4+1)
=1/y^4-3+1/y^4=1/(y^2+1/y^2)^2-5=1/[(y-1/y)^2+2]^2-5
由y2+3y-1=0 两边除以y 代入上式
则 原式=[(-3)^2+2]^2+5=1/126