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

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

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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

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