a + b = 5 a * b = 4
a³ + b³ = (a + b)(a² - ab + b²) = (a + b) * [(a + b)² - 3ab] = 5 * (5² - 3 * 4) =
= 5 * (25 - 12) = 5 * 13 = 65
a³ + b³ = 65
