(c-4)(3c+9)
Distribute the terms in the first set of parentheses over the terms in the second set of parentheses
c (3c + 9) - 4 (3c + 9)
3c^2 + 9c - 12c - 36 combine like terms
3c^2 - 3c - 36
That's a neat way to do " FOIL " ing !!
