x²+x-2=0
则x1+x2=-1
x1x2=-2
所以 1/x1+1/x2
=(x1+x2)/x1x2
=1/2
1/x1*1/x2
=1/x1x2
=-1/2
所以是x²+x/2-1/2=0
即2x²+x-1=0