一道数学题...回答后 设X/(X^2-3X+1)=1,求X^3/(X^6-5X^3+1)的值 ..

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一道数学题...回答后 设X/(X^2-3X+1)=1,求X^3/(X^6-5X^3+1)的值 ..

一道数学题...回答后 设X/(X^2-3X+1)=1,求X^3/(X^6-5X^3+1)的值 ..
一道数学题...回答后
设X/(X^2-3X+1)=1,求X^3/(X^6-5X^3+1)的值 ..

一道数学题...回答后 设X/(X^2-3X+1)=1,求X^3/(X^6-5X^3+1)的值 ..
X/(X^2-3X+1)=1
X^2-4X+1=0
x+1/x=4
(x+1/x)^3=64=x^3+1/x^3+3(x+1/x)
所以x^3+1/x^3=52
X^3/(X^6-5X^3+1)=1/(x^3+1/x^3-5)=1/(52-5)=1/47

X/(X^2-3X+1)=1
X=X^2-3X+1
两边除以X(X不等于0)
1=X+1/X-3
X+1/X=4
令Y=X^3/(X^6-5X^3+1)

1/Y=X^3+1/X^3-5
=(X+1/X)(X^2-1+1/X^2)-5
=4*[(X+1/X)^2-2-1]-5
=4*(4^2-3)-5
=4*13-5
=52-5
=47
Y=1/47
即X^3/(X^6-5X^3+1)=1/47