求(x→+∞)lim((x+5)^0.5-x^0.5)的極限, 能寫出具體過程麼?

求(x→+∞)lim((x+5)^0.5-x^0.5)的極限, 能寫出具體過程麼?


lim[x→+∞] [√(x+5)-√x],有理化,上下乘以[√(x+5)+√x]化簡
=lim[x→+∞] [√(x+5)-√x][√(x+5)+√x]/[√(x+5)+√x]
=lim[x→+∞](x+5-x)/[√(x+5)+√x]
=lim[x→+∞] 5/[√(x+5)+√x],由於分母趨向正無窮大,∴整個分式趨向零
=0



求lim(x->0)3^x的極限值.


這個是連續函數的極限
所以直接把x=0代入即可
答案=1



lim(1/x-1/e^x-1)x趨向於0+


lim(1/x-1/e^x-1)x趨向於0+
=lim(x->0+)(e^x-1-x)/x(e^x-1)
=lim(x->0+)(e^x-1-x)/x²;
=lim(x->0+)(e^x-1)/2x
=lim(x->0+)(e^x)/2
=1/2