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问题: 详细解答

X2-7x+1=0,求x2+x-2的值

解答:

X2-7x+1=0,求x2+x-2

x^2-7x+1=0
==>x^2+1=7x
x^2+x^(-2)
=(x+1/x)^2-2
=[(x^2+1)/x]^2-2
=(7x/x)^2-2
=7^2-2
=47