已知x+1/x=3,求x2/x4+x2+1的值已知x+1/x=3,求x方/x4次方+x方+1的值

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已知x+1/x=3,求x2/x4+x2+1的值已知x+1/x=3,求x方/x4次方+x方+1的值
已知x+1/x=3,求x2/x4+x2+1的值
已知x+1/x=3,求x方/x4次方+x方+1的值

已知x+1/x=3,求x2/x4+x2+1的值已知x+1/x=3,求x方/x4次方+x方+1的值
x+1/x=3
则(x+1/x)^2=3^2=9
x^2+1/x^2+2=9
x^2+1/x^2=7
x^2/x^4+x^2+1
=x^2+1/x^2+1
=7+1=8

x+1/x=3
x+1=3x
2x=1
x=1/2
x^2/x^4+x^2+1
=1/x^2+x^2+1
=1/1/4+1/4+1
=4+1/4+1
=21/4

x+1/x=3两边同时平方:
x^2+1/x^2+2=9.
即:
x^2/x^4+x^2=7.所以:
x^2/x^4+x^2+1=8.答案8.

x+1/x=3
则(x+1/x)^2=3^2=9
x^2+1/x^2+2=9
x^2+1/x^2=7
x^2/x^4+x^2+1
=x^2+1/x^2+1
=7+1=8