a是一元二次方程x2+3x-2的实数根a^2+3a-2=0a^2+3a=2a-3/3a2-6a/[a+2-5/a-2]=a-3/3a2-6a/[(a^2-4-5)/(a-2)]=a-3/3a(a-2)*(a-2)/(a+3)(a-3)=1/3a(a+3)=1/3(a^2+3a)=1/3*2=1/6