顶点坐标为（-2,3）y=a(x+2)^2+3=ax^2+4ax+(4a+3)与x轴交于（x1,0）,（x2,0）则x1,x2是方程ax^2+4ax+(4a+3)=0的两个根所以x1+x2=-4,x1x2=(4a+3)/a|x1-x2|=6所以(x1-x2)^2=(x1+x2)^2-4x1x2=6^216-4(4a+3)/a=3616a-16a...