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Consider the following fur the next two ...

Consider the following fur the next two items that follow:
`f(x) = {{:(3x^(2) + 12x -1, -1 le x le 2),(37-x, 2 lt x le 3):}`
Winch of the following statements are correct?
1. f( x) is continuous at x = 2
2. f(x) attains greatest value at x = 2
3. f(x) is differentiate al x = 2.
Select the correct answer using the code given below:

A

1 and 2 only

B

2 and 3 only

C

1 and 3 only

D

1,2 and 3

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the function \( f(x) \) given in two parts and check the three statements regarding its continuity, maximum value, and differentiability at \( x = 2 \). ### Step 1: Define the function The function is defined as: \[ f(x) = \begin{cases} 3x^2 + 12x - 1 & \text{for } -1 \leq x \leq 2 \\ 37 - x & \text{for } 2 < x \leq 3 \end{cases} \] ### Step 2: Check continuity at \( x = 2 \) To check if \( f(x) \) is continuous at \( x = 2 \), we need to find the left-hand limit (LHL) and right-hand limit (RHL) at \( x = 2 \) and see if they are equal to \( f(2) \). 1. **Calculate \( f(2) \)**: \[ f(2) = 3(2)^2 + 12(2) - 1 = 3(4) + 24 - 1 = 12 + 24 - 1 = 35 \] 2. **Calculate the left-hand limit as \( x \) approaches 2**: \[ \text{LHL} = \lim_{x \to 2^-} f(x) = f(2) = 35 \] 3. **Calculate the right-hand limit as \( x \) approaches 2**: \[ \text{RHL} = \lim_{x \to 2^+} f(x) = 37 - 2 = 35 \] Since LHL = RHL = \( f(2) = 35 \), we conclude that \( f(x) \) is continuous at \( x = 2 \). ### Step 3: Check if \( f(x) \) attains the greatest value at \( x = 2 \) 1. The function \( f(x) = 3x^2 + 12x - 1 \) is a quadratic function that opens upwards (since the coefficient of \( x^2 \) is positive). It is increasing in the interval \([-1, 2]\). 2. The function \( f(x) = 37 - x \) is a linear function that is decreasing for \( x > 2 \). Since \( f(x) \) is increasing up to \( x = 2 \) and decreasing thereafter, the maximum value occurs at \( x = 2 \). ### Step 4: Check differentiability at \( x = 2 \) To check if \( f(x) \) is differentiable at \( x = 2 \), we need to compute the derivatives from both sides and see if they are equal. 1. **Differentiate \( f(x) \) for \( -1 \leq x \leq 2 \)**: \[ f'(x) = \frac{d}{dx}(3x^2 + 12x - 1) = 6x + 12 \] At \( x = 2 \): \[ f'(2) = 6(2) + 12 = 12 + 12 = 24 \] 2. **Differentiate \( f(x) \) for \( 2 < x \leq 3 \)**: \[ f'(x) = \frac{d}{dx}(37 - x) = -1 \] Since \( f'(2) = 24 \) (from the left) and \( f'(2) = -1 \) (from the right), the derivatives do not match. Therefore, \( f(x) \) is not differentiable at \( x = 2 \). ### Conclusion Based on our analysis: 1. \( f(x) \) is continuous at \( x = 2 \) (True). 2. \( f(x) \) attains the greatest value at \( x = 2 \) (True). 3. \( f(x) \) is not differentiable at \( x = 2 \) (False). Thus, the correct statements are 1 and 2. ### Final Answer The correct answer is option A: 1 and 2 only.
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