Question

求方程组2(x-y)/3-x+y/4=-1 6(x+y)-4(2x-y)=16解答过程

Answer 1

2(x-y)/3-x+y/4=-1 (1)
6(x+y)-4(2x-y)=16(2)
(1)×12得8x-8y+2x+3y=-12即-4x-5y=-12(3)
（2）式合并项后得6x+6y-8x+4y=16即-2X+10Y=16 ----(4)
3)式×2+4）式得-8x-10y-2x+10y=-12×2＋16得10x=-8即X=4/5
把X=4/5 代入（4）得-2×4/5+10y=16即10y=88/5得y= Y=44/25

Answer 2

2(x-y)/3-x+y/4=16
2x/3-2y/3-x+y/4=16
-x/3-5y/12=16
x=-5y/4-48
-16(x+y)-4(2x-y)=16
-16x-16y-8x+4y=16
-24x-12y=16
-24*(-5y/4-48)-12y=16
30y+24*48-12y=16
18y=16-24*48
y=-568/9
x=-5y/4-48
=-5*568/(9*4)-48
=710/9-432/9
=278/9

Answer 3

（1）式同×12合并项后为 -4X-5Y=-12 ---(3)
（2）式合并项后为-2X+10Y=16 ----(4)
(3)式×2与（4）式相加消去Y 得X=4/5 代回原式得 Y=44/25