回答:
#lim_(x rarr 0 ^ +)1 / x-(1)/(e ^ x-1)= 1/2#
说明:
让:
#f(x)= 1 / x-(1)/(e ^ x-1)#
#“”=((e ^ x-1) - (x))/(x(e ^ x-1))#
#“”=(e ^ x-1 - x)/(xe ^ x-x)#
然后我们寻求:
#L = lim_(x rarr 0 ^ +)f(x)#
# = lim_(x rarr 0 ^ +)(e ^ x-1 - x)/(xe ^ x-x)#
因为这是一种不确定的形式
#L = lim_(x rarr 0 ^ +)(d / dx(e ^ x-1 - x))/(d / dx(xe ^ x-x))#
# = lim_(x rarr 0 ^ +)(e ^ x-1)/(xe ^ x + e ^ x - 1)#
同样,这是一种不确定的形式
#L = lim_(x rarr 0 ^ +)(d / dx(e ^ x-1))/(d / dx(xe ^ x + e ^ x - 1))#
# = lim_(x rarr 0 ^ +)(e ^ x)/(xe ^ x + e ^ x + e ^ x)#
# =(e ^ 0)/(0 + e ^ 0 + e ^ 0)#
# = 1/2 #