You are right. 2/x+3
Simplify the following:
(2 x - 10)/(x^2 - 2 x - 15)
The factors of -15 that sum to -2 are 3 and -5. So, x^2 - 2 x - 15 = (x + 3) (x - 5):
(2 x - 10)/((x + 3) (x - 5))
Factor 2 out of 2 x - 10:
(2 (x - 5))/((x + 3) (x - 5))
Cancel terms. (2 (x - 5))/((x + 3) (x - 5)) = 2/(x + 3):
Answer: 2/(x + 3)