Answer:
x² + 4xy + 4y²
Explanation:
(x + 2y)² = (x + 2y)(x + 2y)
Each term in the second factor is multiplied by each term in the first factor
(x + 2y)(x + 2y)
= x(x + 2y) + 2y(x + 2y) ← distribute both parenthesis
= x² + 2xy + 2xy + 4y² ← collect like terms
= x² + 4xy + 4y²