Question

解方程组3(x+y)-4(x-y)=4和(x+y)/2+(x-y)/6=1

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Answer 1

解:将(x+y)/2+(x-y)/6=1两边乘6,得
3(x+y)+(x-y)=6 方程1
3(x+y)-4(x-y)=4 方程2
简化以上方程组,得
-x+7y=4
2x+y=3
解以上方程得
x=17/15,y=11/15

Answer 2

1式可化为-x+7y=4
所以x=7y-4
带入另一个式子中得y=11/15,所以x=17/15

Answer 3

(x+y)/2+(x-y)/6=1
x/2+x/6+y/2-y/6=1
2x/3+y/3=1
2x+y=3 (1)
3(x+y)-4(x-y)=4
3x+3y-4x+4y=4
-x+7y=4 (2)
(1)+2*(2)
y+14y=11
y=11/15
x=7y-4=17/15

Answer 4

化简方程 设X+Y = m X-Y=n
3m-4n=4 3m+n=6
得到5n=2
15m=28
得到2x=m+n
x=3217=m-n
y=11/15

Answer 5

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