Answer:
4x² - 28xy + 49y²
Explanation:
(2x - 7y)²
= (2x - 7yy)(2x - 7y)
Each term in the second factor is multiplied by each term in the first factor, that is
2x(2x - 7y) - 7y(2x - 7y) ← distribute parenthesis
= 4x² - 14xy - 14xy + 49y² ← collect like terms
= 4x² - 28xy + 49y²