If the largest interval of x in which the function f x = x 3 - 3 x + 1 is decreasing is a , b , then the value of a + 2 b is equal to

Question

If the largest interval of x in which the function f x = x 3 - 3 x + 1 is decreasing is a , b , then the value of a + 2 b is equal to, – 1, 0, 1, 2

MARKS App · Accepted Answer

As f ' x = 3 x 2 - 3 = 3 x - 1 x + 1 i.e. the largest interval in which f x decreases is - 1,1 ⇒ a = - 1 b = 1 ∴ a + 2 b = 1