{(x,y)x+y=-1}u{(x,y)x-2y=8},求这连个集合的并集,

x.y都是自然数,且x(x-u)-y(y-x)+12,求x.y得值快1且x(x-y)-y(y-x)=12 x/(y+z+u)=y/(z+u+x)=z/(u+y+x)=u(x+y+z)求(x+y)/(z+u)+(y+z)/(y+x)+(z+y)/(x+y)+(u+x)/(z+y) 已知x/(y+z+u)=y/(z+u+x)=z/(u+x+y)=u/(x+y+z)求(x+y)/(z+u)+(y+z)/(x+u)+(z+u)/(x+y)+(u+x)/(y+z) x,y>0,且x+2y=1,u=(x+1/x)(y+1/(4y)最小值是: {(x,y)x+y=-1}u{(x,y)x-2y=8},求这连个集合的并集, U=x^0.5(1+y)^0.5 对y求导. U={y|y=log2x,x>1},P={y|y=1/x,x>2},则CuP= 已知u={y|y=log2X x>1}P={y|y=1/x x>2}求 CuP y=4^x-2^(x+1)+1变形,y=4^x-2^(x+1)+1y=u^2-2u+1u=2^x 这是一道数学题：X+Y-1≤0 X-Y+1≥0 Y≥-1 且U(X,Y)=X²+Y²-4X-4Y+8,则U(X,Y)最小值为多少 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 全集U={(x,y)丨 x,y属于一切实数},集合B={(x,y)丨y不等于x+1},那相对于U,B的补集是如题 du(x,y)=2xycos(x^2y)dx+x^2cos(x^y)dy,求u(x,y) y≥0,x^2 +y^2 =3,u=(y+1)/(x+3) ,求u的最值. 如何matlab求解多元方程x,y,z,u]=solve('48.18577=x/[1+(6280000*x*z)^2]+y/[1+(6280000*y*u)^2]','655.3747=x*{6280000*x*z/[1+(6280000*x*z)^2]}+y*{6280000*y*u/[1+(6280000*y*u)^2]}','49.78774=x/[1+(5709085*x*z)^2]+y/[1+(5709085*y*u)^2]','724.7968=x* 已知x,y∈R*,x+y=xy,求u=x+2y最小值 求全微分 u=x^y^z 帮忙证明个高数题u=x^2*y^2/(x+y),求证 x*u(x)+y*u(y)=3u