根据根与系数的关系可得：
x1+x2=-2
x1*x2=-4
可得：x1²+x2²=(x1+x2)²-2x1*x2=4+8=12
所以：(x1-3)(x2-3)
=x1*x2-3x1-3x2+9
=x1*x2-3(x1+x2)+9
=-4+6+9
=11
x2/x1+x1/x2
=(x2²+x1²)/（x1*x2)
=12/(-4)
=-3