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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】

     

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    如图，在方格纸中，我们把每个小正方形的顶点称为格点，已知点A、B、C都在格点上，且每个小正方形的边长都为1．
    （1）画线段AB，并过点C作CD⊥AB，垂足为点D；
    （2）连结AC、BC．
    ①求△ABC的面积；②已知AB=5，
    求（1）中线段CD的长．

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    13、兰州市“安居工程”新建成的一批楼房都是8层高，房子的价格y（元/平方米）随楼层数x（楼）的变化而变化（x=1，2，3，4，5，6，7，8）；已知点（x，y）都在一个二次函数的图象上（如图所示），则6楼房子的价格为
    2080
    元/平方米．

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    某市“安居工程”新建成的经济房都是8层高，房子的价格y（元/m2）随楼层数x（楼）的变化而变化（x=1，2，3，4，5，6，7，8）；已知点（x，y）都在一个二次函数的图象（如图）上，对称轴方程为：x=4，则6楼房子的价格为
    3080
    3080
    元/m2．

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    已知点A，B，C都在直线l上，且AB=6cm，BC=2cm，则A，C两点的距离是
    4cm或8cm
    4cm或8cm
    ．

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    某市“安居工程”新建成的一批楼房都是8层高，房子的价格y（元/平方米）随楼层数x（楼）的变化而变化（x=1，2，3，4，5，6，7，8）；已知点（x，y）都在一个二次函数的图象上（如图所示），则6楼房子的价格为__________元/平方米

    .

     

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