The number of intersections between the image and the x-axis of the function f (x) = 13x3-x2-3x-1 is______ One

The number of intersections between the image and the x-axis of the function f (x) = 13x3-x2-3x-1 is______ One

The derivative of function is f ′ (x) = x2-2x-3 = (x + 1) (x-3). From F ′ (x) = (x + 1) (x-3) > 0, we can get x > 3 or x < - 1, then the function increases monotonically. From F ′ (x) = (x + 1) (x-3) < 0, we can get - 1 < x < 3, then the function decreases monotonically. So when x = - 1, the function gets the maximum value f (- 1