当x y分之x-y=2时-搜答案-搜搜做题作业网

1/X-1/Y=3分子分母同除以xy=(1/y-2-1/x)/(2/y+3-2/x)=(1*3-2)/(2*3+3)=1/9

少了个中括号?原式=3yx^2-[2xy^2-2(xy-3x^2y/2)+3xy^2]=xy(3x-2y+2-3x/2+3y)=xy(y+3x/2+2)=3*(-1/3)(-1/3+3*3/2+2)=

再问：非常感谢

解3x²y-[2xy²-4(1/2xy-3/4x²y)+xy]+3xy²=3x²y-(2xy²-2xy+3x²y+xy)+3xy&

x/y=3=>x=3y原式=(9y²+2*3y*y-3y²)/(9y²-3y*y+y²)=12/7再问：能不能先化简，后代入？再答：可以是可以，x²+

因为你的题目未表达清楚,所以按两种情况考虑解法1：当x=3,y=7时：(xy+2y)-[(x²-4)/(x-2)]=y(x+2)-(x+2)(x-2)/(x-2)=y(x+2)-(x+2)=

3xy-[2xy-2(xy-2分之3xy)+xy]+3xy=6xy-[2xy-2xy+3xy+xy)=6xy-4xy=2xy=2×3×3分之1=2

xy/(x+y)=2∴xy=2(x+y)(3xy-x-y)/(3x-5xy+3y)=[6(x+y)-x-y]/[3x+3y-10(x+y)]=5(x+y)/[-7(x+y)]=-5/7

解(x^4-y^4)/(x²-2xy+y²)÷(x²+y²)/(y-x)=(x²-y²)(x²+y²)/(x-y)

代数式：=2x^2-3xy+y^2-2xy-2x^2+5xy-2y+1=y^2-2y+1=(y-1)^2当y=-1时代数式=（-2）^2=4

5xy/(2x-y)=2所以10xy/(2x-y)=4所以(2x-y)/(10xy)=1/415xy/(6x-3)=3×5xy/[3(2x-y)]=5xy/(2x-y)=2

原式=xy分之(x²-y²)+x(x-y)分之y(x-y)=xy分之(x²-y²)+x分之y=xy分之(x²-y²+y²)=xy分

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

答案：要想使多项式中不存在xy项,只需要多项式中xy项的系数为0,又题意可得方程：-2k+（1/5）=0解得：k=1/10；

（2x-y）分之5xy与10xy分之（2x-y）的乘积为0.5,前者等于2,后者等于0.25代数式6x-3?没写完?

xy/(x+y)=2(x+y)/xy=1/21/x+1/y=1/2(3x-xy+3y)/(-x+3xy-y)=(3/y-1+3/x)/(-1/y+3-1/x)=[3(1/x+1/y)-1]/[(3-(

值为-6-1分之2+4=-1分之6=-6

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

原式即为A*(x+2y)^2/(x-y)(x+y)=1即A*16/3=1∴A=3/16很高兴为您解答,【学习宝典】团队为您答题.请点击下面的【选为满意回答】按钮,

[(xy+2)(xy-2)-2x的平方y的平方+4]÷（-xy)当x=10,y=25分之1=[x^2y^2-4-2x^2y^2+4]÷（-xy)=[-x^2y^2]÷（-xy)=xy=10*1/25=