2x y等于-2 x-3y=6-搜答案-搜狗做题网

题目有问题

x^+2xy+y^+4=16(x+y)²=16-4=12(1)x^-2xy+y^=16(x-y)²=16(2)(1)-(2)2y*2x=-4xy=-1(3xy+6y^)+|x^-(

4xy加5x²y加yx²再问：谢谢了，

-5x+2-3xy-5y因为xy=1所以原式=-5x-5y-1-5（x+y)-1因为x+y=3所以-15-1=-16

先化简,再求值3x²y-[2xy-2(xy-2/3x²y)+xy]=3x²y-2xy+2(xy-2/3x²y)-xy=3x²y-2xy+2xy-4/3

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

2(x+xy)-[(xy-3y)-x]-(-xy)=2x+2xy-xy+3y+x+xy=3x+3y+2xy=3（x+y）+2xy=3*（-2）+2*3=0

3x²-xy+y²=101-xy+4y²=421-2得3x²-3y²=6x²-y²=2选B

2分之1或负4分之3

1/x-1/y=3则x-y=-3xyx-3xy-y/2x-xy-2y=(-3xy-3xy)/(-6xy-xy)=6/7

（x+2y-xy)-(-2x-y+xy)=x+2y-xy+2x+y-xy=3x+3y-2xy=3(x+y)-2xy=3×0.5-2×(-0.5)=1.5+1=2.5

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

xy/x+y=6∴xy=6(x+y)3x-2xy+3y/-x+3xy-y=[3x-12(x+y)+3y]/[-x+18(x+y)-y]=-9(x+y)/17(x+y)=-9/17再问：你在啊？再答：在

|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

(x+y)²=x²+2xy+y²=(x²-2xy+y²)+4xy=(x-y)²+4xy=49所以x+y=±7x²y+xy²

设x+y=axy=b,则b/a=3b=3a所以-X+3XY-Y分之2X-3XY+2Y可以写成(2a-3b)/(3b-a)=-7/8

∵x=2,y=3∴2(xy^2+3y^3-x^2y)-(-2x^2y+y^3+xy^2)-4y^3=2xy²+6y³-2x²y+2x²y-y³-xy&

不会

原式=-x²y+2xy²+2x²y²-4xy³-3x³+27x³y-18x²y²+2x²y-18x&