这个是初中的题吧,你是要下面的结果吗?
把下列方程改写成用含x的式子表示y的形式
2/3x+2y=1 => y=(1-2/3x)/2
4/1x+4/7y=2 => y=(2-4/1x)*7/4
5x-3y=x+2y => y=4/5x
2(3y-3)=6x+4 => y=x+5/3
用带入法解下列方程组:
(1)
y=x+3
7x+5y=9
=>
7x+5(x+3)=9 => 12x+15=9 => x=-0.5 y=2.5
(2)
3s-t=5
5s+2t=15
=> 5s+2(3s-5)=15 => s=25/11 t=20/11
(3)
3x+4y=16
5x-6y=33
=>
5x-6(4-3/4x)=33 => x=6 y=-0.5
(4)
4(x-y-1)=3(1-y)-2
2/x+3/y=2
=>
4x-4y-4=3-3y-2
2y+3x=2xy
=>
4x-5=y
2y+3x=2xy
=>
2(4x-5)+3x=2x(4x-5)
=>
x1=2 y1=3
x2=0.625 y2=-2.5