We can see the sequence goes by decreasing 9 on each number
so the numbers are
2, -7, -16, -25, -34, -43, -52, -61, -70
so adding all these numbers we get
2-7-16-25-34-43-52-61-70
= -306
hope this helped
The factorization: (x-9) (x+12) (AC method)
X intercepts: (9,0), (-12,0)
Y intercepts: (0, -108)
(13 + 20) + 15 = 13 + (20 + 15)
