解方程组 {(x+y)/2+(x-y)/3=6 5(x+y)-2(x-y)=4
问题描述:
解方程组 {(x+y)/2+(x-y)/3=6 5(x+y)-2(x-y)=4
答
(X+Y)/2+(X-Y)/3=6方程两边同乘以6得3(X+Y)+2(X-Y)=36化简得5x+y=36
4(x+y)-5(x-y)=2化简得9y-x=2解方程组5x+y=36,9y-x=2得x=7y=1
答
(x+y)/2+(x-y)/3=6 ①
5(x+y)-2(x-y)=4 ②
由①得 3x+3y+2x-2y=36 5x+y=36 y=36-5x ③
由②得 5x+5y-2x+2y=4 3x+7y=4 ④
③代入④得 3x+252-35x=4
32x=248
x=7.75
代入③得y=36-5×7.75=-2.75