解下列方程组.(每小题5分,共30分)
(1) (2)
(3) (4)
(5) (6)
(1) (2) (3) (4) (5) (6)
【解析】(1) 解:将②代入①得
···································· 2分
将代入②得························· 4分
∴ 是原方程组的解··························· 5分
(2) 解:①+②得
···································· 2分
将代入①得
···································· 4分
∴ 是原方程组的解··························· 5分
(3) 解:②-①得
···································· 2分
将代入①得
∴ 是原方程组的解··························· 5分
|
由①得 ③
由②得 ④
③+④得 x = 8··························· 3分
将x = 8代入④得 y = 1···························· 4分
∴是原方程组的解···························· 5分
(5) 解:由①得
③································ 1分
由②得
④································ 2分
③×2得 ⑤
④×3得 ⑥
⑤-⑥得
····································· 3分
将y = 1代入④得
····································· 4分
∴ 是原方程组的解···························· 5分
(6) 解:①+②得
③·································· 1分
①-②得
④·································· 2分
③+④得
····································· 3分
将代入③得y = – 2 ··························· 4分
∴ 是原方程组的解 5分
科目:初中数学 来源:2011-2012学年重庆市西南大学附属中学七年级下学期期中考试数学卷(带解析) 题型:解答题
列方程组解下列应用题.(每小题8分,共16分)
(1) 甲、乙两人分别以均匀的速度在400米圆形跑道上跑步,甲的速度较快.当两人反向跑时,每40秒钟相遇一次;当两人同向跑时,每3分20秒相遇一次,求甲、乙两人的速度.
(2) 某市政府决定2012年投入6000万元用于改善医疗卫生服务,比2011年增加了1250万元.投入资金的服务对象包括“需方”(患者等)和“供方”(医疗卫生机构等),预计2012年投入“需方”的资金比2011年提高30%,投入“供方”的资金将比2011年提高20%.该市政府2011年投入“需方”和“供方”的资金各是多少万元?
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