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北京市房山区2015-2016学年七年级数学下学期期中联考试题答案一、选择题（本题共30分，每小题3分）题号12345678910答案CAABCACBBD二、填空题（本题共18分，每小题3分）题号111213141516答案43，229x-1X+y=12(答案不唯一)3，-2m＜8三、解答题（本题共22分，其中17～19题每小题4分，20～21每小题5分）17.解：由①得x=4-y③·····································1分把③带入②得y=3····························2分把y=3带入①得x=1···································3分所以原方程组的解是13xy···································4分18.解：由①×3得6x+9y=36③··························1分由②×2得6x+8y=34④·························2分由③-④得y=2···································3分把y=2带入①得x=3所以原方程组的解是32xy．···································4分19.解：由①得x≥-2………..1分由②得x＜5………………..2分所以不等式组的解集是-2≤x＜5………………………3分所以整数解是-2，-1,0,1,2,3,4…………….4分20.解：原式=x2+x-42–(x2-4)………………………..3分=x2+x-42–x2+4…………………………..4分=x–38……………………………..5分21.解：xxyxx2122=x2+2xy-（x2+2x+1）+2x……………………………...2分=x2+2xy-x2-2x–1+2x=2xy–1………………………………………………3分当251x，25y时原式=2×251×（-25）-1………………………………………..4分=-2………………………………………………………5分22.已知关于x、y的方程组22331xykxyk的解x、y值的和等于6，求k的值。解：方法一、-：x+y=2k–1………………………3分因为：x+y=6所以：2k–1=6………………………..5分K=27……………………………6分方法二、解方程组得:kykx123………..……………..3分因为：x+y=6所以：（3k–2）+（1–k）=6………..5分所以：K=27……………………………6分23.解：设0．8元的邮票买了x枚，2元的邮票买了y枚·····················1分根据题意得130.8220.xyxy，·························4分解得58xy………………………………………………………5分答：0．8元的邮票买了5枚，2元的邮票买了8枚····················6分24.解：设A、B两地相距xkm，乙每小时走ykm，则甲每小时走（y+2）km．·······················1分·········2(2)364(2··············)36114087yyxyyxxy解这根据题意，个方程组得得………………………………5分答：A、B两地相距108km·······················…6分25．解:设该校有宿舍x间,,根据题意,有下面不等式成立:0420818xx此不等式可化为下面不等式组:042081420818xxxx······················3分∴此不等式的解集为5