Step-by-step explanation:
f(x) = x³ - ax² - 13x + b.
f(1) = 1³ - a(1)² - 13(1) + b = 0
=> 1 - a - 13 + b = 0, b - a - 12 = 0.
f(-3) = (-3)³ - a(-3)² - 13(-3) + b = 0
=> - 27 - 9a + 39 + b = 0, 12 - 9a + b = 0.
Therefore, b - a - 12 = 12 - 9a + b. 8a = 24, a = 3.
=> b - (3) - 12 = 0, b = 15.
