先化简,再求值,4y²-(x² y) (x²-4y²),其中x=-28,y=18-搜答案-智慧作业帮

先化简，再求值4x

原式=4(x+4)(x−4)•x−42+xx+4=2x+4+xx+4=x+2x+4；当x=3时，原式=57．

原式=(x²+y²+2xy)(x²+y²-2xy)/(x+y)²=(x+y)²(x-y)²/(x+y)²=(x-y)&#

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

x-3（x+2y）+4（2y-x）=x-3x-6y+8y-4x=-6x+2y=-6×（-3）+2×2=18+4=22

先化简,再求值:【1/（x-y）】-【1/（x+y）】/【xy²/（x²-y²）】,其中x=√2+1,y=√2-1【1/（x-y）】-【1/（x+y）】/【xy²

:[(3x-y)(2x+4y)-(x+2y)(5x-2y)]/4=(x+2y)(6x-2y-5x+2y)/4=x(x+2y)/4当x=-2,y=1时原式=-2(-2+2)/4=0再问：补上一点写漏了，

[x²+y²-(x-y)²+2y(x-y)]÷4y=[x²+y²-(x²-2xy+y²)+2y(x-y)]÷4y=(x²

x√(1/x)+√4y-2分之√x+1/y√y³=√x+2√y-√x/2+√y=3√y当x=4,y=1/9时,原式=3√y=1

原式=8x³+4x²y-4x²y-2xy²+2xy²+y³-8x³+x²y+8xy²-y³=x

：(x-2y)(x+3y)-2(x-y)(x-4y)=x²＋3xy－2xy－6y²－2﹙x²－4xy－xy＋4y²﹚=x²＋xy－6y²－2

原式=1/4y[x^2-4*y^2-(x^2+8*xy+16y^2)]=1/4y(-8*xy-20*y^2)=-2x-5y代入得：原式=(-2)*(-2)-5(-3)=19

(x-2y)(x+3y)-(2x-y)(x-4y)=x²+3xy-2xy-6y²-(2x²-8xy-xy+4y²)=x²+3xy-2xy-6y

原式=(x-y)²/(x+y)²(x+y)^4/(x-y)²*1/(x+y)=x+y=-3

(x-y)^2+7(x+y)-11(x-y)^2-8(x+y),=-10(x-y)²-(x+y)当x+y=-3,x-y=-1时=-10*(-1)²-(-3)=-10+3=-7

（x+y）（2x-y）-（x+2y）（x-2y）=2x2-xy+2xy-y2-（x2-4y2）=2x2-xy+2xy-y2-x2+4y2=x2+xy+3y2；把x=3，y=4代入得，原式=32+3×4

[(5x+3y)^2-(3y+x)(3y-x)^16]/(4x)=【25x^2+30xy+9y^2-9y^2+x^2]/4x=(26x^2+30xy)/4x=13x/2+15y/2=13/2-15/2

原式=(x^2-4y^2-x^2-8xy-16y^2)/(4y)=-5y-2x=-25-4=-29

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.

为你提供精确解答[(x-2y)²-(x+2y)(x-2y)∕(-4y)=[(x^2+4y^2-4xy)-(x^2-4y^2)]/(-4y)=[8y^2-4xy]/(-4y)=-2y+x代入x

(1)=2x-2y-4x-y=-2x-3y=(-2)*(-1/12)-3*(-1/6)=1/6+3/6=2/3(2)=4a+3a²-3+4a三次方+a-4a三次方）=3a²+5a-