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问题 解答题

已知二次函数y=-x2+4x．

（1）用配方法或公式法把该函数化为y=a（x+m）2+k（其中a、m、k都是常数且a≠0）的形式，并指出函数图象的开口方向，对称轴和顶点坐标；

（2）当x满足什么条件时，函数值随着自变量的增大而减小？

答案

（1）y=-（x2-4x），

=-（x2-4x+4）+4，

=-（x-2）2+4，

对称轴为直线x=2，顶点坐标为（2，4）；

（2）∵y=-（x-2）2+4，a＜0，对称轴为直线x=2，

∴当x＞2时，函数值y随着自变量x的增大而减小．

完形填空
完型填空
     John was ten years old, but he was still   1   Grade One. He liked   2  . and didn't work hard   3   his
lessons. His parents always wanted him   4   a good boy.
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     "What did your teacher praised you?" asked his parents.
     She said to Tom "You're the most foolish (愚蠢) student in our class and John is  10   than you."
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选择题

处于正常细胞分裂后期含有10个DNA分子的某细胞，绝不可能出现的情况是[ ]

A．该细胞可能处于减数第一次分裂后期

B．该细胞可能处于有丝分裂后期

C．该细胞可能处于减数第二次分裂后期

D．产生该细胞的生物体细胞中的染色体数目可能是5或10

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