Question

解下列方程組．(每小題5分，共30分)

(1)                           (2)

(3)                (4)

(5)                  (6)

 

Answer 1

(1) (2) (3) (4) (5) (6)

解析:(1) 解：將②代入①得

···································· 2分

將代入②得························· 4分

∴ 是原方程組的解··························· 5分

(2) 解：①＋②得

···································· 2分

將代入①得

···································· 4分

∴ 是原方程組的解··························· 5分

(3) 解：②－①得

···································· 2分

將代入①得

∴ 是原方程組的解··························· 5分

① ②

(4) 解：原方程組變形為     ···················· 1分

由①得   ③

由②得    ④

③＋④得     x = 8··························· 3分

將x = 8代入④得 y = 1···························· 4分

∴是原方程組的解···························· 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

將y = 1代入④得

····································· 4分

∴ 是原方程組的解···························· 5分

(6) 解：①＋②得

 ③·································· 1分

①－②得

 ④·································· 2分

③＋④得

····································· 3分

將代入③得y = –2 ··························· 4分

∴ 是原方程組的解    5分