0.5x+0.7y=35,x+0.4y=40.求x=?,y=?

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0.5x+0.7y=35,x+0.4y=40.求x=?,y=?0.5x+0.7y=35,x+0.4y=40.求x=?,y=?0.5x+0.7y=35,x+0.4y=40.求x=?,y=?0.5x+0.

0.5x+0.7y=35,x+0.4y=40.求x=?,y=?
0.5x+0.7y=35,x+0.4y=40.求x=?,y=?

0.5x+0.7y=35,x+0.4y=40.求x=?,y=?
0.5x+0.7y=35
x+0.4y=40
化简,得 5x+7y=350 ①
5x+2y=200 ②
①-②,得 5y=150
y=30
将y=30代入①,得x=28.

x=28
y=30

x=28
y=30

10x+14y=700 (1)
10x+4y=400 (2)
(1)-(2)
10y=300
y=30
x+0.4*30=40
x+12=40
x=40-12=28

Y=66 X=-22.4