This type of parabola opens either to the left or to the right. The negative makes it open to the left.
128 = 8d, because the product calls for multiplication to be performed.
So find the greatest common factor (GCF), and make it go on the outside. Or, what is the greatest number that will go in all of those numbers. That would be 3 in this case. So you write it as if you made that equation when you distributed a 3.
3 (2x^2 + 9x + 7)
Then you factor more.
3 (2x^2 + 7) (x + 1)
