x^2-3x+2=0
(x-2)(x-1)=0
x=2或x=1
当x=2时
x^2+1/x^2
=2^2+1/2^2
=4+1/4
=17/4
当x=1时
x^2+1/x^2
=1^2+1/1^2
=1+1
=2