一、选择题（每题4分，共32分）1.抛物线y=ax2+bx－3过点（2，4），则代数式8a+4b+1的值为···········（ ）A.－2 B.2 C.15 D.－152.图1是一个横断面为抛物线形状的拱桥，当水面在l时，拱顶（拱桥洞的最高点）离水面2 m，水面宽4 m.如图2建立平面直角坐标系，则抛物线的关系式是·····························································（ ） 图1 图2A.y=－2x2 B.y=2x2 C.y=－ x2 D.y= x23.把抛物线y= x2－1先向右平移1个单位，再向下平移2个单位，得到的抛物线的式为·········································（ ）A.y= (x+1)2－3 B.y= (x－1)2－3 C.y= (x+1)2+1 D.y= (x－1)2+14.二次函数y=ax2+bx+c（a、b、c为数且a≠0）中的x与y的部分值如下表： x－3－2－1012345y1250－3－4－30512给出了结论：（1）二次函数y=ax2+bx+c有最小值，最小值为－3；（2）当－ ＜x＜2时，y＜0；（3）二次函数y=ax2+bx+c的图象与x轴有两个交点，且它们分别在y轴两侧.则其中正确结论的个数是·········································（ ）A.3 B.2 C.1 D.05.若一次函数y=ax+b（a≠0）的图象与x轴的交点坐标为（－2，0），则抛物线y=ax2+bx的对称轴为····································（ ）A.直线x=1 B.直线x=－2 C.直线x=－1 D.直线x=－46.设一元二次程（x－1）（x－2）=m（m＞0）的两实根分别为α，β，且α＜β，则α，β满足···············································（ ）A.1＜α＜β＜2 B.1＜α＜2＜β C.α＜1＜β＜2 D.α＜1且β＞27.若抛物线y=x2－2x+c与y轴的交点为（0，－3），则下列说法不正确的是················································· |
