Thank you!Got stuck after doing what?
The very first thing to do with such a problem at this level is to use the Rational Root Theorem. Since the leading coefficient is 1, this leaves x = +/-1 or x = +/-5 as your ONLY hope to find any Rational Roots. Try them out using whatever method is at your disposal. Also, keep track of your results. They may prove helpful, particularly when you find x = 1 leads to something <0 and x = 5 leads to something >0. That will be important.