Answer:
a² + 2ab + b²
Step-by-step explanation:
(a + b)² = (a + b)(a + b)
multiply each term in the second factor by each term in the first factor
=a(a + b) + b(a + b) ← distribute both parenthesis
= a² + ab + ab + b² ← collect like terms
= a² + 2ab + b²