I guess you mean:
X^2 - X - 6 and X^2 - 5X + 6
X^2 - X - 6 = (X + 2)(X − 3)
X^2 - 5X + 6 = (X − 2)(X − 3)
Based on that, their common factor is:
(X - 3)
9.4m questions
12.2m answers