解下列方程组.(每小题5分,共30分)(1)(2)(3)(4)(5)(6)-七年级数学
题文
解下列方程组.(每小题5分,共30分) (1) (2) (3) (4) (5) (6) |
答案
(1)(2)(3)(4)(5)(6) |
(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
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