x y=91,y-x=63.,y x=46怎么求-搜答案-搜搜考试网

x-xy=8(1)xy-y=-9(2)则有(1)-(2):X-XY-XY+Y=X+Y-2XY=8-(-9)=17

f（x+y,xy）=x^2+y^2

因为f（x+y,xy）=x^2+y^2=（x+y）^2-2xy所以f（x,y）=x^2-2y现对x求导得到：fx(x,y)=2x再对y求导得到：fxy(x,y)=0.所以无论x,y为何值,fxy(x,

原式=(x-y)(x²+2xy+y²-xy)-(x-y)(x²-2xy+y²+xy)=(x-y)(x²+xy+y²)-(x+y)(x&sup

3x*+xy-2y*=0（3x-2y）(x+y)=0那么x=2y/3或x=-yy/x=3/2或x/y=-1(x/y)-(y/x)-(x*+y*)/(xy)=(x/y)-(y/x)-(x/y+y/x)=

x^2+xy+y=14y^2+xy+x=28两式相加x^2+y^2+2xy+x+y=42(x+y)^2+(x+y)-42=0(x+y-6)(x+y+7)=0x+y=6或x+y=-7

=-(xy^2)^4+3(xy^2)^3+(xy^2)^2=-27-27-3=-57

(-3x^y+2xy)-(4x^+xy)=-3x^y+2xy-4x^-xy=-3x^y+xy-4x^所以填上-3x^y+xy-4x^

答：x+y=-1,xy=-2-5（x+y)+(x-y)+x(xy+y)=-5x-5y+x-y+xy(x+1)=-4x-6y+(-2)(x+1)=-4x-6y-2x-2=-6x-6y-2=-6(x+y)

你确定没写错题目?后面的式子一约就变成前面的式子了,答案也是8/xy再问：怎么个约法?再答：y/xyyy约掉剩下1/x

x、y都是整数吧?就按这个解答.方程化为(x-1)(y+1)=17,由于17=1*17=(-1)*(-17),且x、y都是整数,因此可得（1）x-1=1,y+1=17,解得x=2,y=16；（2）x-

（x+y)（x-y)-y^2+（x-y)^2-（6x^2y-2xy^2)÷2y=（x+y)（x-y)-y^2+（x-y)^2-2y（3x^2-xy)÷2y=（x+y)（x-y)-y^2+（x-y)^2

即(x-2y)²=0x-2y=0所以x=2y所以原式=(2x²+2xy-xy-y²)/(4x²-4xy+y²)=(2x²+xy-y²

7或者-8再问：求过程^_^再答：两个等式两边相加

∵x-y=4xy，∴2x+3xy-2yx-2xy-y=2(x-y)+3xyx-y-2xy=8xy+3xy4xy-2xy=112．故答案为：112．

xy+1/xy>=2√（xy*1/xy）=2(当xy=1/xy即xy=1时取等号)x/y+y/x>=2√（x/y*y/x）=2(当x/y=y/x即x=y取等号)当x=y=1时可以同时满足两项的等号要求

X²+2xy+y²/xy乘x²-2xy+y²/xy+y²=(x+y)²/xy×(x-y)²/y(x+y)=(x+y)(x-y)&#

xy=2010,x+y=2009,求x,y

由题意x,y为方程x^2-2009x-2010=0的2个根则x=2010,y=-1或者或者x=-1,y=2010

解方程x*x+xy=y+y*y

令y=kxx*x+kx*x=k*x+k*k*x*x(1-k*k+k)x^2-kx=0x((1-k*k+k)x-k)=0由上式得X=0或(1-k*k+k)x-k=0解得：k=(x-1+（或-）√（（1-

xy>0得x,y同号又因为x+y

[-(x-y)^2/xy]^-4*(y^2-xy/x)^3*(x^4/y^10)÷(xy-y^2/x)^-5=-y(y-x)^29^-x*27^y=3^-2x*3^3y=3^(-2x+3y)=3^(-