用代入法解下列二元一次方程组:(1)2s+3t+4=0,5s+6t+7=0 (2)x/2-y/3=1/3,3(x-1)=y+1(3)3x+2y=4x+3y=1 (4)0.5y+0.2x=1.2,0.3y-0.6=-0.2x
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![用代入法解下列二元一次方程组:(1)2s+3t+4=0,5s+6t+7=0 (2)x/2-y/3=1/3,3(x-1)=y+1(3)3x+2y=4x+3y=1 (4)0.5y+0.2x=1.2,0.3y-0.6=-0.2x](/uploads/image/z/7631230-22-0.jpg?t=%E7%94%A8%E4%BB%A3%E5%85%A5%E6%B3%95%E8%A7%A3%E4%B8%8B%E5%88%97%E4%BA%8C%E5%85%83%E4%B8%80%E6%AC%A1%E6%96%B9%E7%A8%8B%E7%BB%84%EF%BC%9A%EF%BC%881%EF%BC%892s%2B3t%2B4%3D0%2C5s%2B6t%2B7%3D0+%EF%BC%882%EF%BC%89x%2F2-y%2F3%3D1%2F3%2C3%EF%BC%88x-1%EF%BC%89%3Dy%2B1%EF%BC%883%EF%BC%893x%2B2y%3D4x%2B3y%3D1+%EF%BC%884%EF%BC%890.5y%2B0.2x%3D1.2%2C0.3y-0.6%3D-0.2x)
用代入法解下列二元一次方程组:(1)2s+3t+4=0,5s+6t+7=0 (2)x/2-y/3=1/3,3(x-1)=y+1(3)3x+2y=4x+3y=1 (4)0.5y+0.2x=1.2,0.3y-0.6=-0.2x
用代入法解下列二元一次方程组:(1)2s+3t+4=0,5s+6t+7=0 (2)x/2-y/3=1/3,3(x-1)=y+1
(3)3x+2y=4x+3y=1 (4)0.5y+0.2x=1.2,0.3y-0.6=-0.2x
用代入法解下列二元一次方程组:(1)2s+3t+4=0,5s+6t+7=0 (2)x/2-y/3=1/3,3(x-1)=y+1(3)3x+2y=4x+3y=1 (4)0.5y+0.2x=1.2,0.3y-0.6=-0.2x
以(1)为例:
(1)2s+3t+4=0 ①
5s+6t+7=0 ②
由①得t=(-4-2s)/3 ③
把③代入②得
5s+6(-4-2s)/3+7=0
解得 s=1
把s=1代入③得t=(-4-2)/3=-2
∴s=1
t=-2
一下请自己动手先做,有问题再追问.