Question

x+y=6 xy=-2

如果x+y=6 xy=-2 求2x+3y-3xy+(4xy-3x)-(4y-7)的值 要过程，谢谢。

Answer 1

2x+3y-3xy+(4xy-3x)-(4y-7）
合并同类项得:-(x+y)+xy+7
带入已知
x+y=6 xy=-2
得-1

Answer 2

X+Y=6
X=6-Y @ Y=6-X

2X+3Y-3XY+(4XY-3X)-(4Y-7)
=2(6-Y)+3(6-X)-3(-2)+[4(-2)-3(6-Y)]-[4(6-X)-7]
=12-2Y+18-3X+6+[-8-18+3Y]-[24-4X-7]
=12-2Y+18-3X+6+[26+3Y]-[17-4X]
=12-2Y+18-3X+6+26+3Y-17+4X
=(12+18+6+26-17)+[-2Y+3Y]+[-3X+4X]
=45+[1Y]+[1X]
=45+[Y+X]
=45+6
=51

Answer 3

打开括号
2x+3y-3xy+4xy-3x-4y+7
=-x-y+xy+7
=-(x+y)+xy+7
=-6-2+7
=-1

Answer 4

2x+3y-3xy+(4xy-3x)-(4y-7)
=-x-y+xy+7
=-(x+y)+xy+7
=-6+(-2)+7
=-1

Answer 5

2x+3y-3xy+(4xy-3x)-(4y-7)
=2x+3y-3xy+4xy-3x-4y+7
=-x-y+xy+7
=-6-2+7
=-1