lim((x-y)/(x+y))求极限.(x,y)→(0,0)

求极限lim[(sinx-siny)/(x-y)]x趋向y 求极限lim (sinxy) / y x->a y->0 lim(x→0y→1)(1+xe^y)^(2y+x/x)求极限 求极限lim(x→+∞,y→+∞) (X+Y)/(X^2-Y^2) lim((x-y)/(x+y))求极限.(x,y)→(0,0) 求极限lim(x,y)→(+∞,+∞) [(xy)/(x^2+y^2)]^xy.求极限lim(x,y)→(+∞,+∞) [(xy)/(x^2+y^2)]^xy, Lim(Sinx-siny/x-y)极限 求极限：lim (x^2+y^2)^xy（x,y）lim (x^2+y^2)^xy x,y→0 这个极限是多少啊!怎么算? lim(xy/(x^2+y^2))^x^2 x,y趋近无穷 求极限 求极限lim(x,y)→(+∞,+∞) (xy/(x^2+y^2))^x^2 求lim（x+y）/（x*x+y*y）,x和y都趋向无穷大时的极限 lim x^2y^2/x^2y^2+(x-y)^2 这个题的极限怎么求呢.lim x^2y^2/x^2y^2+(x-y)^2(x,y)-(0,0)怎么求极限哦. lim x^2y^2/x^2y^2+(x-y)^2 这个题的极限怎么求呢..lim x^2y^2/x^2y^2+(x-y)^2(x,y)-(0,0)怎么求极限哦.. 求极限lim(x→1 y→2) (x²+y²)/xy 求极限lim(xy)^2/(x^2+y^2)^2,(x,y)趋于（0,0） 求极限 lim((x,y）→（0,0)) (x^2+y^2)sin1/xy lim[1+sin(xy)]^(y/x)x趋于0 y趋于π,求极限 求下列各极限 lim(x,y)→(0,1) (2-xy)/(x^2+2y)