factorise x^5 - 6x^4 + 5x^3 + 16x^2 - 12x - 16 - Wolfram|Alpha

To get the factors, guess a root, use the null factor law, use polynomial long division etc. etc.

eg. Guess x = 1 is a root. Doesn't work. Guess x = -1. It works therefore x + 1 is a factor. Divide x + 1 into x^5 - 6x^4 + 5x^3 + 16x^2 - 12x - 16. Get a quartic factor. Repeat the process.

Not difficult, just drudge work for you to do (not us).