方程组x+y=480 (1+10%)x+(1+20%)y=554 怎么解

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方程组x+y=480 (1+10%)x+(1+20%)y=554 怎么解

方程组x+y=480 (1+10%)x+(1+20%)y=554 怎么解
方程组x+y=480 (1+10%)x+(1+20%)y=554 怎么解

方程组x+y=480 (1+10%)x+(1+20%)y=554 怎么解
x+y=480
所以y=480-x
(1+10%)x+(1+20%)(480-x)=554
1.1x+576-1.2x=554
0.1x=22
x=220
y=480-x=260

X=480-Y 带入(1+10%)X+(1+20%)Y=554
110%(480-Y)+120%Y=554
1.1*480-1.1Y+1.2Y=554
0.1Y=554-528
0.1Y=26
Y=260
X=220

x+y=480
1.1x+1.2y=554
1.1x+1.1y=528
0.1y=554-528=26
y=260
x=480-260=220

===>>x+y=480-------------------------------1
1.1x+1.2y=554-------------------------2
算式2减去算式1
===>> 0.1x+0.2y=554-480=74--------------3
因x+y=480,所以x=480-y,代入算式3
===>> ...

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===>>x+y=480-------------------------------1
1.1x+1.2y=554-------------------------2
算式2减去算式1
===>> 0.1x+0.2y=554-480=74--------------3
因x+y=480,所以x=480-y,代入算式3
===>> 0.1(480-y)+0.2y=74
48-0.1y+0.2y=74
0.1y=74-48
0.1y=26
y=260
x=480-260=220

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