已知x2-3x+1=0,求x3+1/x3的值

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已知x2-3x+1=0,求x3+1/x3的值已知x2-3x+1=0,求x3+1/x3的值已知x2-3x+1=0,求x3+1/x3的值x²-3x+1=0x+1/x-3=0x+1/x=3x

已知x2-3x+1=0,求x3+1/x3的值
已知x2-3x+1=0,求x3+1/x3的值

已知x2-3x+1=0,求x3+1/x3的值
x²-3x+1=0
x+1/x-3=0
x+1/x=3
x²+1/x²=9-2=7
x³+1/x³
=(x+1/x)(x²-1+1/x²)
=3×(7-1)
=18

答案是18
x^2+1=3x
x^3+1/x^3=(x^6+1)/x^3=(x^2+1)(x^4-x^2+1)/x^3=3x*【(x^2+1)^2-3x^2】/x^3=3x*(9x^2-3x^2)/x^3=18
(x^2表示的是x的平方,依次可推其他的 )