Answer:
9x² - 42x + 49
Explanation:
Given
(3x - 7)² = (3x - 7)(3x - 7)
Each term in the second factor is multiplied by each term in the first factor, that is
3x(3x - 7) - 7(3x - 7) ← distribute both parenthesis
9x² - 21x - 21x + 49 ← collect like terms
= 9x² - 42x + 49