Question

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

Solution

Correct option is

Strictly increasing and strictly decreasing x Ïµ (–1, 3) 

 

Given                    f (x) = x3 – 3x2 – 9x + 20

                                         

  

  

Using number line method, as shown in figure

Thus, (x) is strictly increasing for  and strictly decreasing for x Ïµ (–1, 3).

SIMILAR QUESTIONS

Q1

 

  

Local minimum at x = 2, then

 

Q4

 

 a minimum at x= 1 is the value of a is    

 

Q5

Assuming that be petrol burnt in a motor boat varies as the cube of its velocity, the most economical speed when going against a current of ckm/hr is 

Q7

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

Q8

The minimum value of 

Q9

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

Q10

 

Find the interval of increase or decrease of the