Where a is Positive Constant. Find The Interval In Which f’ (x) Is Increasing.

Let f (x) be a function such that f’(a) ≠ 0. Then at x = α ; f (x)

The minimum value of 

Find the interval in which f (x) = 2x³ + 3x² – 12x + 1 is increasing.

Find the interval in which f (x) = x³ – 3x² – 9x + 20 is strictly increasing or strictly decreasing.

Find the interval of increase or decrease of the 

The function f (x) = sin⁴ x + cos⁴ x increasing if:

 Then f decreases in the interval   

Find the interval for which f (x) = x – sin x is increasing or decreasing.

If a < 0, and f (x) = e^ax + e^–ax is monotonically decreasing. Find the interval to which x belongs.