Step-by-step explanation:
Using the identity a² - b² = (a + b) (a - b)
=> (3 {p - q})² - (5 {q - r})²
=> [(3 {p - q}) + (5 {q - r})] [(3 {p - q}) - (5 {q - r})]
=> [(3p - 3q) + (5q - 5r)] [(3p - 3q) - (5q - 5r)]
=> [3p - 3q + 5q - 5r] [3p - 3q - 5q + 5r]
=> [3p + 2q - 5r] [3p - 8q + 5r]
