1.3x+2y+z=13
问题描述：
1.3x+2y+z=13
x+y+2z=7
2x+3y-z=12
2.x+2y+3z=11
x-y+7z=10
x+3y+2z=2
3.若方程组4x+3y=1
ax+（a-1）y=3的解,x、y相等,则a的值为_______
A.4 B.10 C.11 D.12
请说出答案以及解题思路
答
1.3x+2y+z=13 ① x+y+2z=7 ②2x+3y-z=12 ③①+③ 5x+5y=25 ④①×2 6x+4y+2z=26 ⑤⑤-② 5x+3y=19 ⑥④-⑥ 2y=6 y=3 x=2 z=12.x+2y+3z=11 ①x-y+7z=10 ②x+3y+2z=2 ③①-② 3y-4z=1 ④①-③ -y+z=9 ⑤得 y=-37 z=-28...