令t=x^2+x
x^2+x+（1/x^2+x）=2
t+1/t=2
t^2+1=2t
t^2-2t+1=0
(t-1)^2=0
t=1
x^2+x=1
2x^2+2x+1
=2(x^2+x)+1
=2*1+1
=3