根据题意得
x1+x2=-3
x1x2=-1/2
∴1/x1²+1/x2²=(x1²+x2²)/x1²x2²=[(x1+x2)²-2x1x2]/(x1x2)²=[3²-2×(-1/2)]/(-1/2)²=40
2 、(x1+x2)²=9
3、（1+x1)(1+x2)=1+(x1+x2)+x1x2=1+3-1/2=7/2