解方程组:X/30+Y/20+(75-X-Y)/40=2.5 X/30+(75-X-Y)/20+Y/40=2.8
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解方程组:X/30+Y/20+(75-X-Y)/40=2.5 X/30+(75-X-Y)/20+Y/40=2.8
![解方程组:X/30+Y/20+(75-X-Y)/40=2.5 X/30+(75-X-Y)/20+Y/40=2.8](/uploads/image/z/15181360-16-0.jpg?t=%E8%A7%A3%E6%96%B9%E7%A8%8B%E7%BB%84%EF%BC%9AX%2F30%2BY%2F20%2B%2875-X-Y%29%2F40%3D2.5+X%2F30%2B%2875-X-Y%29%2F20%2BY%2F40%3D2.8)
X/30+Y/20+(75-X-Y)/40=2.5 4X+6Y-3X-3Y =X+3Y=2.5*120-75*3
X/30+(75-X-Y)/20+Y/40=2.8 4X+3Y-6X-6Y =-2X-3Y=2.8*120-75*6
-X=5.3*120-75*9 X=75*9-5.3*120=3(3*75-53*4)=3*13=39
3Y=2.5*120-75*3 Y=2.5*40-75=25
X/30+(75-X-Y)/20+Y/40=2.8 4X+3Y-6X-6Y =-2X-3Y=2.8*120-75*6
-X=5.3*120-75*9 X=75*9-5.3*120=3(3*75-53*4)=3*13=39
3Y=2.5*120-75*3 Y=2.5*40-75=25
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