x-y x y分之2y的平方

3x^2+xy-2y^2=(3x-2y)(x+y)=0x=-2y/3,或x=-y但由于你要求的式子中分母里有X平方-Y平方x=-y舍去其他就代入吧

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

（x的平方-y的平方)分之2xy+(x+y)分之x-(y-x)分之y=（x的平方-y的平方)分之2xy+(x+y)分之x+(x-y)分之y=(x²-y²)分之[2xy+x(x-y)

∵正数x，y满足2x+y-3=0，∴3=2x+y．∴x+2yxy=13(2x+y)(1y+2x)=13(5+2xy+2yx)≥13(5+22xy•2yx)=3，当且仅当x=y=1时取等号．则x+2yx

=-(x+2y)(x-2y)/(x+y)²×2x(x+y)/(x-2y)=-2x(x+2y)/(x+y)=-(2x²+4xy)/(x+y)

2x+3y=53y=5-2xy=(5-2x)/33x^2+12xy+y^2=3x^2+12x(5-2x)/3+(5-2x)^2/9x=4时=48-48+1=1

（x分之x-y）-（y分之x+y）+（2xy分之x的平方-y的平方）=1-y/x-1-x/y+(x^2-y^2)/2xy=-2(y^2+x^2)/2xy+(x^2-y^2)/2xy=-(x^2+3y^

y=3x/5原式=x/(x+3x/5)+(3x/5)/[x-3x/5]-(9x^3/25)/(x^3-9x^3/25)=8/3-3/2-9/16=29/48

(1)XxX+yxy=(x+y)^2-2xy=4^2+2*12=16+28=44(2)XxXxy+Xxyxy=xy*(x+y)=4*(-12)=-48不懂可追问,有帮助请采纳,谢谢!

原式=[2x/(x-y)]*[y/(x+y)]-[x^4/(x^4-y^4)]/[x^2/(x^2+y^2)]^2=2xy/(x^2-y^2)-(x^2+y^2)^2/[(x^2+y^2)(x^2-y

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

|3-y|+|x+y|=0，且|3-y|≥0，|x+y|≥0，所以3-y=0，x+y=0，所以y=3，x=-3．所以x+yxy=-3+3-3×3=0-9=0．答：x+yxy的值为0．

分式2x+3yxy中，x、y的值都扩大到原来的2倍，则分式的值缩小为原来的12，故选：B．

(x^2-4y^)\(x+y)^2乘以2x(x+y)/(x+2y)=2x(x-2y)\(x+y)

（x/2y）²×（y/2x）-x/y²÷（2y²/x）=x²/2y×（y/2x）-（x/y²）×（x/2y²）=x/8y-x²/（

原式=[(x+y)/(x-y)]^2*[2(x-y)/5(x+y)-[X/(x^2y^2)]/[x/(x+y)]=2/5-[x/(x^2y^2)]*[(X+y)/x]=2/5-(x^2y^2)/(x+

平方差=[(3x-2y)/2+(3x+2y)/2][(3x-2y)/2-(3x+2y)/2]=[(3x-2y+3x+2y)/2][(3x-2y-3x-2y)/2]=3x*(-2y)=-6xy

x的平方-64y的平方分之2x-x-8y分之1=[2x-(x+8y)]/(x-8y)(x+8y)=(x-8y)/(x-8y)(x+8y)=1/(x+8y)

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x-y分之2x的平方-y-x分之x的平方-4xy+x-y分之2y的平方-x的平方=2x/(x-y)-(x²-4xy)/(y-x)+(2y-x²)/(x-y)=(2x+x²