Answer:
3(f - 9)(f + 4)
Explanation:
Assuming you require to factorise the expression
3f² - 15f - 108 ← factor out 3 from each term
= 3(f² - 5f - 36) ← factor the quadratic
Consider the factors 0f the constant term (- 36) which sum to give the coefficient of the f- term (- 5)
The factors are - 9 and + 4 , since
- 9 × 4 = - 36 and - 9 + 4 = - 5 , then
f² - 5f - 36 = (f- 9)(f + 4)
Then
3f² - 15f - 108 = 3(f - 9)(f + 4)