Question

若x+1/x=3,则计算x^2/x^4+1.

Answer 1

因为X+1/x=3,

所以（x+1/x）^2=9

x^2+2+1/x^2=9 x^2+1/x^2=7

两边同时乘x^2

x^4+1=7x^2 x^4=7x^2-1

把上式带入后

x^2/7x^2-1+1=1/7