4(x y )-5(x-y)等于2

X+Y=5,XY=2,5X+4Y-3X-2Y+XY=2X+2Y+XY=2(X+Y)+XY=2×5+2=12.

（2X-3Y-2XY)-(X-4Y+XY)=2X-3Y-2XY-X+4Y-XY=X+Y-3XY因为x加y等于110,xy等于33所以原式等于：110-33*3=11

y分之x等于3分之4--------------------------这题分母是y,分子是x2x²+3xy-5y²分之3x²-5xy+2y²---------

原方程=（2X+5y）*（x-y）分之（3X-2y）*（x-y）=2X+5y分之3x-2y②并且X/Y=4/3所以3X=4yX=4/3*y①把①带入②可得=6\23这个解法是原方程先化简的...比较简

由　1/X-1/Y=5,两边同乘　XY,得出Y-X=5XY,那么　　分子　-X+XY+Y=6XY分母　2X+7XY-2Y=7XY-2(Y-X)=-3XY　　得此分式的值为－再问：还有一题x+x分之一=

(8x²y-2xy²-3y³)分之(6x³-5x²y-4xy²)=[y(8x²-2xy-3y²)分之x(6x²

因为x+y除以xy等于4,所以,x+y=4xy2x-5xy+2y=2(x+y)-5xy=2*4xy-5xy=3xyx+2xy+y=4xy+2xy=6xy所以,2x-5xy+2y除以x+2xy+y的值＝

2X^2-xy-5x+y+4=o可化为：（x^2-4x+4）+(X^2-XY-X+Y)=0(X-2)^2+(x-Y)(x-1)=0因为x>=YY>=1所以X-Y>=0x-1>=0又因为(X-2)^2>

x分之1-y分之1=4(xy)分之(y-x)=4y-x=4xyx-y=-4xy(x-2xy-y)分之(2x+xy-2y)=[(x-y)-2xy]分之[2(x-y)+xy]=(-4xy-2xy)分之(-

1/X-1/Y=4Y-X=4XY(2X+XY-2Y)/(X-2XY-Y)=[2(X-Y)+XY]/[(X-Y)-2XY]=7/6

通分1/x-1/y=(y-x)/xy=3y-x=3xyx-y=-3xy原式=[(x-y)-2xy]/[5(x-y)+3xy]=(-3xy-2xy)/(-15xy+3xy)=-5xy/(-12xy)=5

2xy(x^5y^2-3x^3y-4x)=2x²y[(x²y)²-3(x²y)-4]∵x²y=3∴原式=2×3×(3²-3×3-4)=-24

（5xy-2x^2）-3xy-2（3xy-4x^2）=5xy-2x^2-3xy-6xy+8x^2=-4xy+6x^2x等于1,y等于-2原式=-4*1*（-2）+6*1^2=8+6=14

原式可化简为xy(-x^2-y^2+2xy)=xy(-x^2-y^2-2xy+4xy)=xy(-(x+y)^2+4xy)注：-x^2-y^2-2xy=-（x+y）将1,2式代入得,3*（-（-5）^2

题出错了吧

上下同乘33xy=y-x代入替换掉3xy加减下约掉x-y得13/7

由已知条件可得：x-y=-4xy,（也就是在等式两边乘xy后整理,即可）,代入所求的式子里分母为-4xy+7xy,即3xy；分子为-4xy-2xy,即-6xy,化简得-2

1/x-1/y=2(y-x)/xy=2y-x=2xy(3x+5xy-3y)/(x-xy-y)=[5xy-3(y-x)]/[-xy-(y-x)]=(5xy-6xy)/(-xy-2xy)=-xy/-3xy

|x-y|=4,xy=-3(x+y)^2=(x-y)^2+4xy=14-12=2x+y=根2,-根2xy^2+x^2y=xy(x+y)=-3根2,3根2再问：(x+y)^2=(x-y)^2+4xy=1

3x²y²-[5xy²-(4xy²-3)+2x²y²]=x²y²-xy²-3