Argh!! Really stuck!! Please help

Hi all, I'm having a few problems doing practical problems. I can solve some of them but I'm having problems with deaccelleration in particular.. Can you help me solve these problems?

The distance **s** travelled by a train in **t** seconds after it applies its brakes is given by http://itsligo.learnonline.ie/filter...18de7c5420.gif. How far has the train travelled before it comes to rest ?

I'm totally stumped by this one but I can do some acceleration questions, such as:

A missile is fired vertically upwards and its height **h** in metres after time **t **is given by http://itsligo.learnonline.ie/filter...68c9726d40.gif. Calculate the maximum height reached by the missile.

I know thw anwer to this is 1000.. But I'm lost with deaccelleration..

Can someone please help, thanks in advance.