x1+x2=2
x1x2=-5/2
所以
x1²+x2²
=(x1+x2)²-2x1x2
=4+5
=9
x2/x1+x1/x2
=(x2²+x1²)/x1x2
=9/(-5/2)
=-18/5
(x1-x2)
=x1²+x2²-2x1x2
=9+5
=14
（x1-1/x1）（x2-1/x2）
=x1x2-x1/x2-x2/x1+1/x1x2
=x1x2+1/x1x2-(x2/x1+x1/x2)
=-5/2-2/5+18/5
=7/10