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