Answer:
see explanation
Explanation:
(9m + 4)² - (9m - 4)² ← expand both factors using FOIL
= 81m² + 72m + 16 - (81m² - 72m + 16) ← distribute parenthesis by - 1
= 81m² + 72m + 16 - 81m² + 72m - 16 ← collect like terms
= 144m
= 72(2m)
which is divisible by 72 for all m