Show that limx→0x|x| does not exist.
Let f(x)=x|x|. then
limx→0+f(x)limh→0f(0+h)=limh→0f(h)=limh→0h|h|=limh→0hh=1.
limx→0−f(x)limh→0f(0−h)=limh→0f(h)=lim−h→0h|−h|=limh→0−hh=−1.
∴limx→0+f(x)≠limx→0−f(x).
Hence, limx→0−f(x) does not exist.
Show that limx→0e−1x does not exist.