Question
Find the intervals in which the following functions are strictly increasing or strictly decreasing:
2x3 – 8x2 + 10x + 5
Solution
Let f (x) – 2x3 – 8x2 + 10x + 5
∴ f ' (x) = 6x2– 16x + 10 = 2 (3x2 – 8x + 5) = 2 (x – 1) (3x – 5)
For f (x) to be increasing,
f ' (x) > 0 ⇒ 2 (x – 1) (3x – 5) > 0 ⇒ (x – 1) (3 x – 5) > 0
For f(x) to be decreasing,
