Hello this is Ana from Period 4. Somethings that you should be careful with Decomposition is when foiling to be very careful with the positive and negative signs. You must be very careful with the simple mistakes because they can change your entire answer. Also don't forget to distribute the A, B, and C to the corresponding parts. When combining like terms be sure to set it equal to the like term that is in the original equation. To make sure that everything is correct just plug it into your graphing calculator by pressing 2nd matrx, edit set to a 3x4 scale, put in all your values, 2nd quit, 2nd matrx, math, RREF, 2nd matrx again, enter, and close parenthesis. I hope that this helped.
Thank you.