Short Answer TypeFind 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.Â
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 decreasingÂ
Find the intervals in which the function f (x) = 2x3 – 15x2 + 36x + 1 is
(a) strictly increasing   (b) strictly decreasingÂ
Let f (x) = 2x3 – 15x2 + 36x + 1
f ' (x) = 6x2 – 30x + 36 = 6 (x2 – 5 x + 6) = 6 (x – 2) (x – 3)
(a)Â For f (x) to be increasing, f' (x) > 0
i.e., 6 (x – 2) (x – 3) > 0 or (x – 2) (x – 3) > 0
⇒  either x < 2 or x > 3
∴  f (x) is increasing in x < 2 or x > 3.
(b)Â For f (x) to be decreasing, f ' (x) < 0
i.e. 6 (x – 2) (x – 3) < 0. or (x – 2) (x – 3) < 0
⇒  2 < x < 3
∴  f (x) is decreasing in 2 < x < 3
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 – 2x3Â
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