當x→0 y→1時求lim(1-xy)/x²;+y²;

當x→0 y→1時求lim(1-xy)/x²;+y²;


lim(1-xy)/x²;+y²;
=lim(1-0)/0+1
=1



求lim sin(xy)/xy,x趨近於2,y趨近於0


首先,你要知道極限值:lim(s->0)sin s / s = lim(s->0)cos s / 1 = cos 0 = 1(用到了洛必達法則)lim(x->2,y->0)sin(xy)/xy = lim(y->0)sin(2y)/(2y)(換元2y = s)= lim(s->0)sin s / s = 1….



lim[(x^2+x-1)^1/2-(x^2-2x+3)^1/2]當x趨向負無窮


看成一分之[(x^2+x-1)^1/2-(x^2-2x+3)^1/2]然後上下同時乘以[(x^2+x-1)^1/2+(x^2-2x+3)^1/2]化簡為(3x-4)\[(x^2+x-1)^1/2+(x^2-2x+3)^1/2]這時候分子分母同時除以x分子=3-4\x=3分母=2(簡單自己算一下就行)最…