Answer:
option 3
Explanation:
Given
(6a + b)²
= (6a + b)(6a + b)
Each term in the second factor is multiplied by each term in the first factor, that is
6a(6a + b) + b(6a + b) ← distribute both parenthesis
= 36a² + 6ab + 6ab + b² ← collect like terms
= 36a² + 12ab + b²