大一高等数学多元函数求极限 第三大题前三题

Question

如题所述

Answer 1

Answer 2

(1)lim(x,y)→(0,0)(2-√(4-xy))/xy
=lim(x,y)→(0,0) [2²-(4-xy)]/xy·[2+√(4-xy)]
=lim(x,y)→(0,0) xy /xy·[2+√(4-xy)]
=lim(x,y)→(0,0) 1/[2+√(4-xy)]
= 1/4

(2) lim(x,y)→(0,?) 看不清楚