练习册

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    已知点A(a.).B(2a.y).C(3a.y)都在抛物线上. (1)求抛物线与x轴的交点坐标, (2)当a=1时.求△ABC的面积, (3)是否存在含有.y.y.且与a无关的等式?如果存在.试给出一个.并加以证明,如果不存在.说明理由. 解:(1)由5=0.·············································································· 得.．·················································································· ∴抛物线与x轴的交点坐标为(0.0).(.0)．······································· (2)当a=1时.得A.B.C.······························ 分别过点A.B.C作x轴的垂线.垂足分别为D.E.F.则有 =S - - ···················································· =--···································· =5········································································ (3)如:． ········································································· 事实上. =45a2+36a． 3()=3[5×(2a)2+12×2a-(5a2+12a)] =45a2+36a．············ ∴． ···················································································· 【查看更多】

     

    题目列表(包括答案和解析)

    一张试卷25题，若做对了一题得4分，做错了一题扣1分，小李做完此卷后得70分，则他做对的题目数是（　　）
    A、18B、17C、19D、20

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    21、有一益智游戏分二阶段进行，其中第二阶段共有25题，答对一题得3分，答错一题扣2分，不作答得0分．若小明已在第一阶段得50分，且第二阶段答对了20题，则下列哪一个分数可能是小明在此益智游戏中所得的总分（　　）

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    2、本卷第17～25题的9道题中，每道题所赋分数（注：分值依次为6，7，7，8，8，8，9，9，10）的众数和中位数分别是（　　）

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    9、一张试卷上有25道选择题：对一道题得4分，错一道得-1分，不做得-1分，某同学做完全部25题得70分，那么它做对题数为（　　）

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    一本练习册内有24份练习卷，总共有426道练习题，每份练习卷中有25题或20题或16题．那么这本练习册中有25题的练习卷的份数为（　　）
    A、1B、2C、3D、4

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