a² - b² = (a - b)(a + b)
(a - b)² = a² - 2ab + b²
a³ - b³ = (a - b)(a² + ab + b²)
232² - 231² = (232 - 231)(232 + 231) = 463
148² - 2*148*48 + 48² = (148 - 48)² = 100² = 10000
(81² - 31²)/(81² + 81*31 + 31²) = (81 - 31)(81² + 81*31 + 31²)/(81² + 81*31 + 31²) = 50
