解方程组 {3(x+y)-4(x-y)=11 {2(x-y)+5(x+y)=27

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解方程组{3(x+y)-4(x-y)=11{2(x-y)+5(x+y)=27解方程组{3(x+y)-4(x-y)=11{2(x-y)+5(x+y)=27解方程组{3(x+y)-4(x-y)=11{2(

解方程组 {3(x+y)-4(x-y)=11 {2(x-y)+5(x+y)=27
解方程组 {3(x+y)-4(x-y)=11 {2(x-y)+5(x+y)=27

解方程组 {3(x+y)-4(x-y)=11 {2(x-y)+5(x+y)=27
化简得:-x+7y=11① 7x+3y=27②
①式×7得:-7x+49y=77 ③
②+③得:52y=104
∴y=2
代入①得:x=3
∴x=3,y=2

{3(x+y)-4(x-y)=11
{2(x-y)+5(x+y)=27 .
解得
{x+y=5,
{x-y=1.
∴{x=3,
{y=2.

原式化简得x+y=5,x-y=1.
∴x=3,y=2.

{3(x+y)-4(x-y)=11 {2(x-y)+5(x+y)=27
得 {-x+7y=11 {7x+3y=27
{x=3 {y=2

∴{x=3
y=2

根据4(X+Y)=27;x-y=3列出二元一次方程组的应用题