求Lim[(xy+1)^0.5-1]/(x+y) x->0 y->0的极限

求下列各极限 lim(x,y)→(0,1) (2-xy)/(x^2+2y) 求极限lim(x,y)→(0,0) [1-cos(xy)]/xy^2. 跪求极限Y=lim (xy+1)/x^4+y^4,当（x,y）→（0,0）, 求二重极限lim[xy/(1+x^2+y^2)],x→0,y→0.求详细步骤 求极限lim(1-cosxy)/x²y²,xy都趋于0 求极限：1)x趋于0,y趋于1时,lim(1-xy)/(x^2+y^2) lim(x→0y→1)(1+xe^y)^(2y+x/x)求极限 求极限lim x→0 y→0 2xy/根号下1+xy 然后-1 {不在根号里｝ 求极限:lim xy分之{[(1+xy)开3次根号]-1},(x,y)→(0,0) 求极限lim(xy)^2/(x^2+y^2)^2,(x,y)趋于（0,0） 求极限lim(x→1 y→2) (x²+y²)/xy 求极限(工本高数）lim [2-(xy+4)^(1/2)]/xyx->0y->0证明函数f(x,y)=(x+y)/(x-