Answer:
D
Step-by-step explanation:
Given
a² - 36 = 5a ( subtract 5a from both sides )
a² - 5a - 36 = 0
Consider the factors of the constant term (- 36) which sum to give the coefficient of the a- term (- 5)
The factors are - 9 and + 4 , since
- 9 × + 4 = - 36 and - 9 + 4 = - 5 , then
(a - 9)(a + 4) = 0 ← in factored form
Equate each factor to zero and solve for a
a - 9 = 0 ⇒ a = 9
a + 4 = 0 ⇒ a = - 4
solution is { - 9, 4 } → D
