因为抛物线的顶点为(-1,4),所以可设抛物线的解析式为y=a(x+1)^2+4 = ax^2+2ax+a+4设抛物线与x轴交与两点A(x1,0),B(x2,0),则AB=6所以|x1-x2|=6两边平方可得：(x1-x2)^2 = 36即：x1^2 -2*x1*x2 + x2^2 = 36,所以(x1+x2...