Question

解方程组2(x-y)/3-x+y/4=-1 6(x+y)-4(x-y)=12 怎样能简便一点解 ？

Answer 1

解方程组2(x-y)/3-(x+y)/4=-1， 6(x+y)-4(x-y)=12，怎样能简便一点解 ？
解：2(x-y)/3-(x+y)/4=-1...........(1)
6(x+y)-4(x-y)=12...............(2)
由(2)得2(x-y)-3(x+y)=-6..........(3)
由(1)得8(x-y)-3(x+y)=-12........(4)
(4)-(3)得6(x-y)=-6，故x-y=-1...........(5)
将(5)代入(3)式得3(x+y)=-2+6=4，故x+y=4/3.......(6)
(5)+(6)得2x=1/3，故x=1/6；代入(6)得y=4/3-x=4/3-1/6=7/6.

Answer 2

2(x-y)/3-x+y/4=-1,8(X-Y)-3(X+Y)=-12,5X-11Y=-12
6(x+y)-4(x-y)=12 ,2X+10Y=12,X+5Y=6,5X+25Y=30,36Y=42,Y=7/6,X=1/6