验证当x→1时(1-x^3)⼀(2+x)与1-x是等价无穷小

2025-03-10 22:56:50
推荐回答(1个)
回答1:

lim(x→0)
[ln√(1+x/1-x)]
/
x
=lim(x→0)
(1/2x)*ln[(1+x)/(1-x)]
=1/2
lim(x→0)
[ln(1+x)-ln(1-x)]
/
x
(因为x→0时,ln(1+x)→0、ln(1-x)→0

x→0,上下同时求导)
=1/2
lim(x→0)
[ln(1+x)]'/x'
-1/2
lim(x→0)
[ln(1-x)]'/x'
=1/2
lim(x→0)
1/(1+x)
-1/2
lim(x→0)
[-1/(1-x)]
=1/2
[1/(1+0)]
+
1/2
[1/(1-0)]
=1/2
+
1/2
=1
所以,当x→0时无穷小量ln√(1+x/1-x)与x是等价无穷小