【正文】
? x = 3y =- 2z =- 7 D .????? x = 7y = 5z =- 3 D 三元一次方程組的應(yīng)用 自我診斷 3. 3 .甲、乙、丙三個(gè)數(shù)的和是 36 ,甲數(shù)比乙數(shù)的 2 倍大 1 ,乙數(shù)的12恰好等于丙,則甲、乙、丙三個(gè)數(shù)分別為 ( ) A . 29, 8,4 B . 21, 10,5 C . 19, 9,8 D . 10, 5,21 B 1 .下列選項(xiàng)中,是三元一次方程的是 ( ) A . xy + z = 11 B . x +2y- z = 6 C . 7 x - y + 3π = 4 D . 2 x + 5 y - 4 z = 3 D 2 .方程組??? x ∶ y ∶ z = 1 ∶ 2 ∶ 3x + y + 2 z = 54的解是 ( ) A.????? x = 6y = 12z = 18 B .????? x = 18y = 12z = 6 C .????? x = 3y = 6z = 9 D .????? x = 9y = 6z = 3 A 3 .在 ①????? x = 3y = 0z = 0, ②????? x = 1y = 1z = 0, ③????? x = 0y =- 1z = 0這三對(duì)數(shù)值中, 是方程 x+ 2 y + z = 3 的解, 是方程 2 x - y - z = 1 的解, 是方程 3 x - y - z = 2的解,因此 是方程組????