14: You should get
The fraction is a standard ratio of a power and exponential, we know that it converges to zero, which can be easily confirmed using the l'Hospital rule.
What about the exponential with polynomial in the exponent? There are two possibilities. One is to go back one step, when it was a ratio of two exponentials. This fraction is of the form "infinity over infinity", so l'Hospital might help. Actually, it does not. Try it to see that derivatives cannot get rid of exponentials, so it will only make things worse.
So what is the right way? In the polynomial in the exponent, the x2 prevails and so the exponential goes to zero. This is easily worked out by factoring out. Do it.