已知x+1/x=3,求x^2+1/x^2和(x-1/x)^2的值RT,求解答,要过程,急,谢谢!

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已知x+1/x=3,求x^2+1/x^2和(x-1/x)^2的值
RT,求解答,要过程,急,谢谢!

答:
x+1/x=3
x^2+1/x^2=(x+1/x)^2-2=3^2-2=9-2=7
(x-1/x)^2=x^2-2+1/x^2=7-2=5
所以:
x^2+1/x^2=7
(x-1/x)^2=5