3x+7y=-5 x=y+5 2x-3y=-7 x-3y=-5 2元一次方程

来源：学生作业帮助网编辑：作业帮时间：2024/04/27 20:49:41

3x+7y=-5 x=y+5 2x-3y=-7 x-3y=-5 2元一次方程
3x+7y=-5 x=y+5 2x-3y=-7 x-3y=-5 2元一次方程

3x+7y=-5 x=y+5 2x-3y=-7 x-3y=-5 2元一次方程
依题意得：｛3x+7y=-5①
x=y+5②
把②代入 ①得：
3（y+5）+7y=-5
3y+15+7y=-5
10y=-20
y=-2
把y=-2代入②得：
x=-2+5
x=3
∴｛x=3
y=-2

3x + 7y = -5
3x = -5 - 7y
7y = -5 - 3x
x = -(5 + 7y) / 3
y = -(5 + 3x) / 7

x = y + 5
y = x - 5

2x - 3y = -7
2x = 3y - 7
3y = 2x + 7
x = (3y - 7) / 2
y = (2x + 7) / 3

x - 3y = -5
x + 5 = 3y
x = 3y - 5
y = (x + 5) / 3

3x+7y=-5 (1)
x=y+5 (2)
(2)代入(1)得
3y+15+7y=-5
10y=-20
y=-2
把y=-2代入(2)得
x=3
∴x=3
y=-2

2x-3y=-7 (1)
x-3y=-5 (2)
由(2)得

全部展开

3x+7y=-5 (1)
x=y+5 (2)
(2)代入(1)得
3y+15+7y=-5
10y=-20
y=-2
把y=-2代入(2)得
x=3
∴x=3
y=-2

2x-3y=-7 (1)
x-3y=-5 (2)
由(2)得
x=3y-5 (3)
把(3)代入(1)得
6y-10-3y=-7
3y=3
∴y=1
把y=1代入(3)得
x=-2
∴x=-2
y=1

收起

这是两道题吗
如果是的话
第一题 x=3, y=-2
第二题x=-2, y=1

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 3x+5y-(x+y)=6 2(x+y)-3x=-7 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)= 3(x-y)把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)=3(x-y)²-4(x-y)+7(x-y)-6(x-y)²= 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 x-y/7 - x+y/10 =1/2 2(x-y)-5(x+y)=3修改、、、、（x-y)/7-(x+y)/10=1/2 2(x-y)-5(x+y)=3 把(x-y)看做一个整体,合并同类项5(x-y)+2(x-y)-4(x-y)=3(x-y)次方-4(x-y)+7(x-y)-6(x-y)次方= {2x+y/3-2y=0 2(2x+y)-5=7y