先化简再求值(x y)(x-y)-(4x的三次方y-8xy的立方)÷2xy-搜答案-搜狗做题网

原式=（x-y）（x+2y）除以（x-y）（x-y）-(1-x方y的四次方)-x方y的四次方=(x+2y)除以（x-y）-1当x=根3+根2,y=根3-根2上式=（3倍根3-根2）除以（2倍根2）-1

3x^y漏掉了一个2次方吧3x^2y-[2x^2y-3(2xy-x^2y)-xy]=3x^2y-2x^2y+3(2xy-x^2y)+xy=3x^2y-2x^2y+6xy-3x^2y+xy=3x^2y-

解y=3分之√3吗?原式=(x²-y²)-(2xy)(2x²-4y²)/(2xy)=x²-y²-2x²+4y²=3y&#

(x²+xy-2y²/x²-2xy+y²)-(1-xy²)(1+xy²)-x²÷1/y^4=【（x+2y)(x-y)/(x-y)&

3（x-2y）+2（3x+y）=9x-4y（3x²y-2xy²）-（xy²-2x²y)=xy（3x-2y）-xy(y-2x)=xy(5x-3y)=22

xy^3÷(-xy)+(x+2y)(x-2y)=-y^2+x^2-4y^2=x^2-5y^2=2-5=-3再问：不好意思啊！题目......再答：题目怎么了，不影响结果啊。平方还是正的

解3x平方y-[2xy-2(xy-3/2x平方y)+xy]=3x平方y-(2xy-2xy+3x平方y+xy)=3x平方y-(xy+3x平方y)=3x平方y-3x平方y-xy=-xy=-3×(-1/3)

化简为3xy²(xy+2y²)求得24再问：过程呢

原式=2xy^2-4y+xy-xy-3xy^2+4y=-xy^2=-4×（1/2）^2=-1

等于-2吧

2x²+（-x²+3xy+2y²）-（-x²-xy+2y²）=2x²-x²+3xy+2y²+x²+xy-2y&

原式=-x³y²+2x4次方y²+4x³y²=3x³y²+2x4次方y²把x=2,y=-1代入得原式=3×2³

3（xˆ2y-2xy+x）-2（2x+5xˆ2y-xyˆ2)=3x²y-6xy+3x-4x-10x²y+2xy²=2xy²-8x&

[2x（x^2y-xy^2）+xy(xy-x^2)]÷x^2y=(2x^3y-2x^2y^2+x^2y^2-x^3y)÷x^2y=(x^3y-x^2y^2)÷x^2y=x-y=2008-2004=4

[2x（x^2y-xy^2）+xy(xy-x^2)]÷（x^2y）=[2x²y(x-y)+x²y(y-x)]÷(x²y)=2(x-y)+(y-x)=x-y已知x=2008

1.先化简再求值（½x²y＋1／5xy²－¼xy)·(-½xy²),其中x=-2y=-½（½x²y＋1／5xy

(6x√y/x+3/y*√xy^3)-(4x√x/y+√36xy)=6√（xy)+3√（xy)-4x/y*√（xy)-6√（xy)=(3-4x/y)√(xy)x=3/2,y=27时,原式=（3-2/9

(2x-3y+5xy)-(x-4y-3xy)=2x-3y+5xy-x+4y+3xy=2x-x-3y+4y+5xy+3xy=x+y+8xy=(x+y)+8(xy)=-3+8*(-4)=-3-32=-35

原式=1/9x²y²(2x²y-xy²-2x²y+2xy²)=1/9x²y²*xy²=1/9x³y&

原式=(x+y)(x-y-x+2y)/y=(x+y)y/y=x+y因为已知代数式无意义,即：0的0次方无意义,所以3x-2y-7=0及2x+3y+4=0,解得：x=1,y=-2代入x+y=-1