Answer:
c² - 14cd + 49d²
Step-by-step explanation:
Given
(c - 7d)²
= (c - 7d)(c - 7d)
Each term in the second factor is multiplied by each term in the first factor, that is
c(c - 7d) - 7d(c - 7d) ← distribute both parenthesis
= c² - 7cd - 7cd + 49d² ← collect like terms
= c² - 14cd + 49d²
