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
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.