Answer:
21n² - 28n + 7
Step-by-step explanation:
Each term in the second factor is multiplied by each term in the first factor, that is
3n(7n - 7) - 1(7n - 7) ← distribute both parenthesis
= 21n² - 21n - 7n + 7 ← collect like terms
= 21n² - 28n + 7
