(1)x+y=420,30%x+40%y=160×80% (2)x-y/7-x+y/6=1/2,2(x-y)-5(x+y
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(1)x+y=420,30%x+40%y=160×80% (2)x-y/7-x+y/6=1/2,2(x-y)-5(x+y)+1=0,求方程组解嗷嗷嗷!
(1)由原方程化简得
x+y=420①,0.3x+0.4y=128②
①-②×2.5得x-0.75x=420-320
0.25x=100
x=400
把x=400代入①得y=20
∴x=400,y=20
(2)由原方程化简整理得
-x-13y=21①
-3x-7y=-1②
①×3-②得-39y+7y=64
-32y=64
y=-2
把y=-2代入①得
-x+26=21
x=5
∴x=5 y=-2
x+y=420①,0.3x+0.4y=128②
①-②×2.5得x-0.75x=420-320
0.25x=100
x=400
把x=400代入①得y=20
∴x=400,y=20
(2)由原方程化简整理得
-x-13y=21①
-3x-7y=-1②
①×3-②得-39y+7y=64
-32y=64
y=-2
把y=-2代入①得
-x+26=21
x=5
∴x=5 y=-2
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