用加减法解方程组:1、x+1/3=y+2/4 4x+3y=142、x+y/3+x-y/2=6 3(x+y)-2(x-y)=28

问题描述:

用加减法解方程组:1、x+1/3=y+2/4 4x+3y=14
2、x+y/3+x-y/2=6 3(x+y)-2(x-y)=28

(1)(x+1)/3=(y+2)/4通分4(x+1)=3(y+2)整理得(3)4x-3y=2
(2) 4x+3y=14与(2)相减
6y=12
y=2 代入到(2)
4x=14-3y=8
x=2
(1)x+y/3+x-y/2=6
(2)3(x+y)-2(x-y)=28
(1)(x+y )/3 + (x-y)/2=6 通分2(x+y)+3(x-y)=36——2x+2y+3x-3y=36整理得(3)
(2)3(x+y)-2(x-y)=28——3x+3y-2x+2y=28 整理得(4) x+5y=28
(3)5x-y=36 两边×5得(5)
(5)25x-5y=180 与(4)相加
26x=208
x=8 代入到(3)
y=5x-36=40-36=4