2020一2022英语周报七年级下册新目标(YBC)答案

参考范文：Together the neighbors sent the boys home.The parents of the children who had just arrived from workwere totally shocked to be informed of what had happened.They clearly knew what would have resulted in if itwere not for the neighbors timely help.They were very grateful to the neighbors who had helped to rescue thechildren and expressed their thankfulness again and again.Of course,all the neighbors sang high praise for whatI had done in that dangerous situation.I was very happy that I had been part of this act of neighborliness.It was a dangerous but unforgettablemoment,one I will always keep in mind.The neighbors there did not just stand by in time of danger.Instead,they reacted quickly.The neighbors,from whom I should learn,had been great.They had helped people in needwithout hesitation.I went home with a good feeling.After I shared my experience with my family,they wereshocked to hear it too.They were all for what I had done,and thumbed up for me.

19.解:(1)根据图中建立的空间直角坐标系易知点D,N,M的坐标分别为D(0,0,0),N(20),M(1,2,3)(3分)(2)由空间两点间的距离公式,可得|MD(1-0)2+(20)2+(3-0)2HMN|=√(12)2+(2-1)2+(3-0)2=√11(6分3)在xOy平面上,依题意可设点P的坐标为(2y,y,0),其中y∈[0,1]则|MP|=√(2y-1)2|(y-2)2+(0-3)25y=8y+=√(-)+5当时,线段MP取得最小值,为当y=0时,线段MP取得最大值,为√14故MP的长度的范围为33,41(12分)

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