Mathematics : Application of Derivatives

Find the intervals in which the following functions are strictly increasing or decreasing:
6 – 9x – x ²

Find the intervals in which the following function is increasing or decreasing:
x³ – 6x² + 9x + 15. 

Find the intervals in which the following function f(x) is
(a) increasing      (b) decreasing:
f (x) = 2x³ – 9x² + 12x + 15

Determine the values of x for which the function f(x)  =  2x³ – 24x + 5 is increasing or decreasing.

Find the intervals in which the functions f (x) = 2x³ – 15x² + 36x + 1 is strictly increasing or decreasing. Also find the points on which the tangents are parallel to the x-axis.

Find the intervals in which the function
f(x) = x³ – 12x² + 36x + 17 is
(a) strictly increasing    (b) strictly decreasing 

Find the intervals in which the function f (x) = 2x³ – 15x² + 36x + 1 is
(a) strictly increasing     (b) strictly decreasing 

Find the intervals in which the following functions are strictly increasing or strictly decreasing:
x³ – 6x² – 36x +4

Find the intervals in which the following functions are strictly increasing or strictly decreasing:
2x³ – 15x² + 36x + 6

Find the intervals in which the following functions are strictly increasing or strictly decreasing:
6 + 12x + 3x² – 2x³