This video shows the method to factor a trinomial with a negative sign in the front. The first step is to make the first term positive. This is done by taking the negative sign out. Then we see the middle term of the trinomial. The coefficient of the middle term is a positive one in the example shown. We have to group the coefficient of the first and third term in a way so that the difference is positive one. The appropriate combination is chosen so that this becomes true. In this way the trinomial is separated into its factors.