若x减3y等于4，xy等于-1，求-搜答案-神马作文网

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

x^2-3xy-4y^2=0(x-4y)(x+y)=0x=4y或x=-yx:y=4或-1

1/x-1/y=4(y-x)/xy=4x-y=-4xy(3X+5xy-3y)/(x-3xy-y)=[3(x-y)+5xy]/[(x-y)-3xy]=(-12xy+5xy)/(-4xy-3xy)=1

若X>1,y>0,且满足xy=x^y,x/y=x^(3y)相乘得x2=x^(4y)y=0.50.5x=根号x0.25x2=xx=4x+y=4.5

解析：

x分之1减y分之1等于2（y-x）xy=2y-x=2xyy减xy减x分之3x加xy减3y=[3(x-y)+xy]/(y-x-xy)=(-6xy+xy)/(2xy-xy)=-5xy/xy=-5

3x-4y=4xy=13/y-4y=43-4y^2=4y4y^2+4y-3=0y=1/2,x=2;y=-3/2,x=-2/3所以当y=1/2,x=23x+4y=8当y=-3/2,x=-2/33x+4y

4x+2xy+y等于

题出错了吧

那就会等于-7X+5(X+Y)-3xy-10y=5(x+y)-10XY-10Y=5(x-y-2xy)=-35再问：7X去哪里了，10xy那一步没看懂再答：打错了，应该是-7XY+5(X+Y)-3xy-

(1/x)-(1/y)=3===>(y-x)/(xy)=3===>y-x=3xy===>x-y=-3xy所以,原式=[(x-y)-2xy]/[2(x-y)+3xy]=(-3xy-2xy)/(-2*3x

4xy=(x+y)^2-(x-y)^2xy=〔(x+y)^2-(x-y)^2〕÷4运用这个,在进行计算.

xy+1/xy+y/x+x/y=[(xy)^2+1+x^2+y^2]/(xy)=[(xy)^2-2xy+1+x^2-2xy+y^2+4xy]/(xy)=[(xy-1)^2+(x-y)^2+4xy]/(

1/x-1/y=3y-x=3xyx-y=-3xy(5x-xy-5y)/(x-xy-y)=(-15xy-xy)/(-3xy-xy)=4

悬赏分给我

x分之1减y分之1等于31/x-1/y=3(y-x)/xy=3y-x=3xy所以x-xy-y分之5x-xy-5y=（-3xy-xy）分之(-15xy-xy)=-4分之（-16）=4

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

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

x²+y²=x²-xy+y²+xy=3+5=82x²+xy+3y²=2x²-2xy+3y²+3xy=2(x²-