这方程怎么解答的啊,一道而已,0.9x-y=1800.8x-y=-240解得x=4200,y=3600

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这方程怎么解答的啊,一道而已,0.9x-y=1800.8x-y=-240解得x=4200,y=3600这方程怎么解答的啊,一道而已,0.9x-y=1800.8x-y=-240解得x=4200,y=36

这方程怎么解答的啊,一道而已,0.9x-y=1800.8x-y=-240解得x=4200,y=3600
这方程怎么解答的啊,一道而已,
0.9x-y=180
0.8x-y=-240
解得x=4200,y=3600

这方程怎么解答的啊,一道而已,0.9x-y=1800.8x-y=-240解得x=4200,y=3600
∵0.9x-y=180
   0.8x-y=-240
 ∴9x-10y=1800 ①
  8x-10y=-2400 ②
 ①-②:x=1800-(-2400)
  ∴x=4200
 将x=4200代入①得:9×4200-10y=1800
  y=3600
因此,x=4200
   y=3600

(1)-(2)得:0.1x=420
解得;x=4200 再代入(1)得:y=3600

左右两边分别相减,0.1x=420,x=4200,y=3600