Answer:
- (b - 9)(b + 8)
Explanation:
72 + b - b² ← factor out - 1 from each term and rearrange into standard form
= - (b² - b - 72) ← factor the quadratic
Consider the factors of the constant term (- 72) which sum to give the coefficient of the b- term (- 1)
The factors are - 9 and + 8
Use these factors to split the b- term
b² - 9b + 8b - 72 ( factor the first/second and third/fourth terms )
b(b - 9) + 8(b - 9) ← factor out (b - 9) from each term
(b - 9)(b + 8)
Then
72 + b - b² = - (b - 9)(b + 8)