lim _((x, y)arrow (1,0)) (ln (1+xy))/(y) = ( ).

计算lim _((x,y)arrow (0,0))dfrac (xy)(sqrt {xy+1)-1}=_____________计算_____________

6.求下列各极限:-|||-(1) lim _((x,y)arrow (0,1))dfrac (1-xy)({x)^2+(y)^2} :-|||-(3) lim

6.求下列各极限:-|||-(1) lim _((x,y)arrow (0,1))dfrac (1-xy)({x)^2+(y)^2} ;-|||-(3) lim

lim _(xarrow y)dfrac (1-xy)({x)^2+(y)^2}-|||-bigcirc (3) lim 1-√(xy+1)-|||-y)→(0

lim _(x arrow 2) (sin xy)/(y) = ( )A. $\infty$B. 0C. 1D. 2

(6) =((1+xy))^y;

求下列各极限:(1) lim_((x,y)to(0,1))(1-xy)/(x^2)+y^(2);(3) lim_((x,y)to(0,0))(2-sqrt(xy

4.证明:(1) lim _((x,y)arrow (0,0))dfrac (x+y)(x-y) 不存在;(2)-|||-lim _((x,y)arrow (0

求下列函数的偏导数:-|||-(5) =ln tan dfrac (x)(y);-|||-(6) =((1+xy))^y;-|||-(7) =(x)^dfrac

lim _(x arrow 1) (x-y)/(x^2)-y^(2)=A. 0 ;B. $\frac{1}{2}$ ;C. $\infty$ ;D. 不存在.