Answer:
a₁ = 5
a₂ = - 1
Step-by-step explanation:
3a² - 12a = 15
3a² - 12a - 15 = 0 | : 3
a² - 4a - 5 = 0
a² + a - 5a - 5 = 0
a(a + 1) - 5(a + 1) = 0
(a - 5)(a + 1) = 0
a - 5 = 0 => a₁ = 5
a + 1 = 0 => a₂ = - 1
