Answer:
x² + 4xtx + 4t²
Explanation:
Given
(x + 2t)² = (x + 2t)(x + 2t)
Each term in the second factor is multiplied by each term in the first factor, that is
x(x + 2t) + 2t(x + 2t) ← distribute both parenthesis
= x² + 2tx + 2tx + 4t² ← collect like terms
= x² + 4tx + 4t²