b/a+a/b=ab*(b/a+a/b)=b^2+a^2=(a+b)^2-2ab=3^2+2*(-2)=3^2-4=9-4=5不好意思刚才写错了希望对你有帮助~
b/a+a/b=b^2/(ab)+a^2/(ab)=(a^2+b^2)/(ab)=(a^2+b^2+2ab-2ab)/(ab)=[(a^2+b^2+2ab)-2ab]/(ab)=[(a+b)^2-2ab]/(ab)=[3^2-2*(-2)]/(-2)=(9+4)/(-2)=-13/2