Question Details

In the closed interval [0, 3], the minimum value of the function f given below is:


f(x) = 2x3 −9x2 +12x

Options

A

0

B

4

C

5

D

9

Show Answer

Correct Answer :

Option A

0

Solution :

The correct option is 0.

To find the minimum value of the function f(x)=2x3-9x2+12x in the closed interval [0, 3], we need to evaluate the function at its critical points within the interval and at the endpoints of the interval.

Step 1: Find the critical points of the function.
A critical point occurs where the first derivative f'(x) is equal to zero or is undefined.
Let's find the first derivative of f(x) with respect to x:
f'(x)=ddx(2x3-9x2+12x)
f'(x)=6x2-18x+12

Now, set the derivative to zero to find the critical points:
6x2-18x+12=0
Divide the entire equation by 6 to simplify:
x2-3x+2=0
Factor the quadratic equation:
(x-1)(x-2)=0
This gives the critical points:
x=1 and x=2

Both of these critical points, x=1 and x=2, lie within the given closed interval [0, 3].

Step 2: Evaluate the function at the critical points and the endpoints.
We need to calculate f(x) at x=0, x=1, x=2, and x=3.

1. At the left endpoint, x=0:
f(0)=2(0)3-9(0)2+12(0)=0

2. At the critical point, x=1:
f(1)=2(1)3-9(1)2+12(1)=2-9+12=5

3. At the critical point, x=2:
f(2)=2(2)3-9(2)2+12(2)=2(8)-9(4)+24=16-36+24=4

4. At the right endpoint, x=3:
f(3)=2(3)3-9(3)2+12(3)=2(27)-9(9)+36=54-81+36=9

Step 3: Compare the values to find the absolute minimum.
Comparing the calculated values of f(x):
- f(0)=0
- f(1)=5
- f(2)=4
- f(3)=9

The smallest of these values is 0, which occurs at the endpoint x=0. Therefore, the minimum value of the function on the closed interval [0, 3] is 0.

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