求极限lim(x→+∞,y→+∞) (X+Y)/(X^2-Y^2)

求极限lim(x→+∞,y→+∞) (X+Y)/(X^2-Y^2) 求极限lim(x,y)→(+∞,+∞) [(xy)/(x^2+y^2)]^xy.求极限lim(x,y)→(+∞,+∞) [(xy)/(x^2+y^2)]^xy, 求极限lim x→∞ (x/(1+x))^x 求极限lim(x,y)→(+∞,+∞) (xy/(x^2+y^2))^x^2 x→∞ lim(cosx+x)/(sinx-x) 求极限? 高数 极限 lim x→∞ 求下面的极限lim x→∞ 求极限lim x→-∞ xe^x=?lim x→-∞ xe^x=? 求极限lim(x→0)sinxsin(1/x);lim(x→∞)(arctanx/x) 求极限：lim(x→+∞)[ln(x+1)-lnx] lim(x→+∞)(2/π*arctanx)^x求极限 求极限lim(2/π*arctanx)^x x→∞ 求极限解题lim(x→∞)=arctanx/x lim x→∞ xsin(1/x)求极限 lim(x→∞) xsin(5/x)求极限 lim(-xe^x) x→-∞ 求极限lim(-xe^x) x→-∞ 怎么求极限 (x→∞,y→∞)lim(x^2+y^2)÷(arctanx+(x-y)^2)求极限 求极限 lim(x→ +∞,y→ +∞) (x^2+y^2)/(x^4+y^4)? 求极限,lim(x→+∞)[1+1/(2x)]^x求上式极限,