其中x=-2,y=3

[(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y=(4x^2+4xy+y^2+y^2-4x^2-8xy+2y^2)/4y=(-4xy+4y^2)/4y=-x+y=-1/2+1/3

原式=(9x²+24xy+16y²-4x²+y²-5x²+6xy-y²)÷(-2y)=(30xy+16y²)÷(-2y)=-15x

[（5X+2Y)(3X+2Y)+(X-2Y)(X+2Y)]/4X=[15x²+10xy+6xy+4y²+x²-4y²]/4x=[16x²+16xy]/

原式可化为[(15x²+16xy+4y²)+(x²-4y²)]/4x=(16x²+16xy)/4x=4x+4y代入得4×2+4×3=20

原式=x2+4xy+4y2-2（x2-y2）+2xy-6y2=x2+4xy+4y2-2x2+2y2+2xy-6y2=-x2+6xy，当x=-2，y=12时，原式=-（-2）2+6×（-2）×12=-4

[[(x-2y)²+(x-2y)(x-2y)-2x(2x-y)]÷2x=(x^2-4xy+4y^2+x^2-4xy+4y^2-4x^2+2xy)÷2x=(-2x^2-6xy+8y^2)÷2x

x+y)(x-y)+(x-y)^2-(6x^2y-2xy^2)/2y=x^2-y^2+x^2-2xy+y^2-3x^2+xy=-x^2-xy=-(-2)^2-(-2)(1/3)=-4+2/3=-10/

（2x+(y-1)）(2x-(y-1))=4x^2-(y-1)^2(3x+y)(3x-y)=9x^2-y^2相减得4x^2-y^2+2y-1-9x^2+y^2=-5x^2+2y-1带入得-5*1/25

先一个一个的展开括号项,再同项合并就行了啊[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x=[xx-xy-(xy-yy)+x(x-y)+y(x-y)]÷2x=[xx-xy-xy+yy+xx-

原式=[(x-y)(x-y)+(x+y)(x-y)]/2x=(x-y)(x-y+x+y)/2x=(x-y)·2x/2x=x-y=3-1.5=1.5

解(x-y)(x+y)-(x-2y)²+x(3x-5y)-(x-y)(x-2y)=(x²-y²)-(x²-4xy+4y²)+(3x²-5xy

（x+2y-xy)-(-2x-y+xy)=x+2y-xy+2x+y-xy=3x+3y-2xy=3(x+y)-2xy=3×0.5-2×(-0.5)=1.5+1=2.5

为你提供精确解答先化简：（x^2-y^2-x^2+2xy-y^2+2xy-6y^2)/(-4y)=(4xy-8y^2)/(-4y)=-x+2y=-1-4=-5其他的正在为你解答.

(3x-y)²+(3x+y)(3x-y)=(3x-y+3x+y)(3x-y)=6X(3X-y)=6(3+2)=30

原式=[(5x²+8xy-4y²)-(9x²-4y²)]÷4x=(-4x²+8xy)÷4x=-x+2y当x=2,y=-1时原式=-2-2=-4

（线性规划）由条件当X=Y=3时有最大值Z=6即得K=3再由X+2Y>=0很容易求得Z最小值-3

(x+2y)²-(2x+y)(2x-y)-5y(y-x)=x²+4xy+4y²-(4x²-y²)-(5y²-5xy)=x²+4xy

[3x^2-2x(x+y)+y(2x-y)]÷(x+y)=[3x^2-2x^2-2xy+2xy-y^2]÷(x+y)=(x^2-y^2)÷(x+y)=(x+y)(x-y)÷(x+y)=x-y=1/2-

(2x+3y)^2-(2x+3y)(2x-3y),=(2x+3y)(2x+3y-2x+3y)=6y(2x+3y)=12xy+18y²当x=3,y=1时原式=36+18=54