题目

— Oh, my God! I just missed the last bus back home. — That's really bad. I'm sure you ______ it, but you just didn't hurry up. A . had caught B . could have caught C . could catch D . can catch 答案：B如图，抛物线y=ax2+bx+c的开口向下，与x轴交于点A（﹣3，0）和点B（1，0）．与y轴交于点C，顶点为D． （1）求顶点D的坐标．（用含a的代数式表示）； （2）若△ACD的面积为3． ①求抛物线的解析式； ②将抛物线向右平移，使得平移后的抛物线与原抛物线交于点P，且∠PAB=∠DAC，求平移后抛物线的解析式．