设x>1,y>0,若x^y+x^-y=2根号2,则x^y-x^-y等于A根号6 B根号2 C-2 D2若m^3/2+m^-1/2=4,则(m^3/2-m^-3/2)/(m^1/2-m^-1/2)=?化简 (a^1/2-b^1/2)/(a^1/2+b^1/2)+(a^1/2+b^1/2)/(a^1/2-b^1/2)=?

设x大于1,y大于0,x^y+x^-y=2根号二,x^y-x^-y等于? 设Z=X+Y,其中X,Y满足X+2Y>=0,X-Y 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y 设x,y满足约束条件x+y>=1,x-y>=-1,2x-y 设x>0,y>0,x+y=1,求8/x+2/y的最小值 设随机变量（X,Y)~f(x,y)=1,0 设随机变量(X.Y)～f(x,y)=1,0 设实数x,y满足 x>=0 x-2y>=0 x-y-2 设x,y满足约束条件x>=0 x>=y 2x-y 设x+2y=1,(x,y属于R),若x,y>=0求x2+y2的最大值. 设y=ln(1-2x),则y''(0). 设y=ln(1+2x),则y(0) 设y=ln(1-2x),则y''(0)... 设平面点集A={(x,y)|(y-x)(y-1/x)>=0},B={(x,y)|(x-1)^2+(y-1)^2 设平面点集A={(x,y)|(y-x)(y-1/x)>=0},B={(x,y)|(x-1)^2+(y-1)^2 设平面点集A={(x,y)|(y-x)(y-1/x)>=0},B={(x,y)|(x-1)^2+(y-1)^2 设变量x,y满足约束条件 {x-y≥0,x+y≤1,x+2y≥0},则函数Z=2x+y 的最大值? 设变量x,y满足约束条件 {x-y≥0,x+y≤1,x+2y≥0},则函数Z=2x+y 的最大值?