You may want to review factoring polynomials first.
One case where it's easy to factor a polynomial is when it's the difference of two squares. For example, the polynomial 4x2 − 9y2 is the difference between 4x2 (the square of 2x) and 9y2 (the square os 3y). So it factors as 2x + 3y (the sum of the two things you have the squares of) times 2x − 3y (their difference).
This only works for the difference of two squares. You generally can't factor the sum of two squares.
Again, the polynomial I give you to factor might have a GCD. Be sure to factor it out first.