如图，抛物线y=x 2 +bx+c与x轴交于A（-1，0）、B（3，0）两点。 （1）求该抛物线的解析式； 如图，抛物线y=x 2 +bx+c与x轴交于A（﹣1，0）和...
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| 解：①将点A(-1，0)， B(3，0)代入y=x 2 +bx+c中得： ②解:设p点的纵坐标为t ③存在 ∵点A，B关于抛物线的对称轴对称∴连接BC与对称轴的交点Q就能使 周长最小 设直线BC解析式为：y=kx+b，又∵C(0，-3) B(3，0) ∴y=x-3 又∵抛物线对称轴为x=1 ∴Q（1，-2） |
