题目内容
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
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