The limit of the function is
.
definition of limit :
,
if for every number of
, there exists a
such number
whenever
.
Consider
.

Consider
.

Observe the relation between
and
.

.
must be in terms of
, with no other variables depending on it.
Consider
.

value is minimum when
is maximum, Hence
.
From the above, the restrictions are
and
.
Then the obtained relation is
.
.