19: After substituting the limit point into the given expression you should get
This is an indeterminate ratio. Formally the l'Hospital rule can be used now, but check that it does not help. Try to imagine what happens with the expression as x goes to infinity.
The rest is analogous to
this hint
Hint on limit at
Hint on limit at
1 from the left
Hint on limit at
1 from the right
Answer