x方+x-1=0的根是x1,x2
所以x1²+x1-1=0
x2²+x2-1=0
又韦达定理,x1x2=-1
所以(x1²+2x1-1)(x2²+2x2-1)
=(x1²+x1-1+x1)(x2²+x2-1+x2)
=(0+x1)(0+x2)
=x1x2
=-1