Question

解下列方程组．(每小题5分，共30分)
(1)                           (2)
(3)                (4)
(5)                  (6)

Answer 1

(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

① ②

(4) 解：原方程组变形为     ···················· 1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