已知X+Y=6,xy=3求代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)的值

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已知X+Y=6,xy=3求代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)的值已知X+Y=6,xy=3求代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)的值已知X+Y=

已知X+Y=6,xy=3求代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)的值
已知X+Y=6,xy=3求代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)的值

已知X+Y=6,xy=3求代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)的值
先把代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)化简
(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)
=5XY+4X+7Y+6X-3XY-4XY+3Y
=-2XY+10X+10Y
=-2XY+10(X+Y)
当X+Y=6,XY=3时
原式=-2*3+10*6
=-6+60
=54

打开代数式,得-2XY+10X+10Y,=-2XY+10(X+Y),又因为X+Y=6,XY=3,所以原式=-2*3+10*6=54