由韦达定理得到：x1+x2=-5/2 x1x2=-7/2∴x1²+x2²=（x1+x2）²-2x1x2=25/4+7=53/4x2/x1+x1/x2=(x1²+x2²)/(x1x2)=(53/4)÷(-7/2)=-53/14
