用加减消元法解下列方程(1)4s+3t=5 2s-t=5 (2)5X-6y=9 7x-4y=-5 (3)4x-3y=14 5x+3y=31 (4) 3(x-1)=y+5(4)3(x-1)=y+5 5(y-1)=3(x+5)

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用加减消元法解下列方程(1)4s+3t=52s-t=5(2)5X-6y=97x-4y=-5(3)4x-3y=145x+3y=31(4)3(x-1)=y+5(4)3(x-1)=y+55(y-1)=3(x

用加减消元法解下列方程(1)4s+3t=5 2s-t=5 (2)5X-6y=9 7x-4y=-5 (3)4x-3y=14 5x+3y=31 (4) 3(x-1)=y+5(4)3(x-1)=y+5 5(y-1)=3(x+5)
用加减消元法解下列方程(1)4s+3t=5 2s-t=5 (2)5X-6y=9 7x-4y=-5 (3)4x-3y=14 5x+3y=31 (4) 3(x-1)=y+5
(4)3(x-1)=y+5 5(y-1)=3(x+5)

用加减消元法解下列方程(1)4s+3t=5 2s-t=5 (2)5X-6y=9 7x-4y=-5 (3)4x-3y=14 5x+3y=31 (4) 3(x-1)=y+5(4)3(x-1)=y+5 5(y-1)=3(x+5)
(1)4s+3t=5
2s-t=5
1式-2式×2,得
3t+2t=5-10
t=-1
1式+2式×3,得
4s+6s=5+15
s=2
(2)5X-6y=9
7x-4y=-5
1式×2-2式×3,得
10x-21x=18+15
x=-3
1式×7-2式×5,得
-42y+20y=63+25
y=-4
(3)4x-3y=14
5x+3y=31
1式+2式,得
4x+5x=14+31
x=5
1式×5-2式×4,得
-15y-12y=70-124
y=2
(4) 3(x-1)=y+5
5(y-1)=3(x+5)
1式变形为:3x-3=y+5 ==》3x-y=8
2式变形为:5y-5=3x+15 ==》3x-5y=-20
3式+4式,得
-y-5y=8-20
y=2
3式×5-4式,得
15x-3x=40+20
x=5