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Consider the following function for the ...

Consider the following function for the next two items that follow:
`f(x) = {{:(3x^(2) + 12x -1, -1 le x le 2),(37-x, 2 lt x le 3):}`
Which of the following is/are correct?
1. f(x) is increasing in the interval [-1,2]
2, f(x) is decreasing in the interval (2.3)
Select the correct answer using the code given below:

A

1 only

B

2 only

C

Both 1 and 2

D

Neither 1 nor 2

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the piecewise function given and determine whether the statements about its increasing and decreasing behavior are correct. ### Step 1: Define the function The function is given in piecewise form: - For the interval \([-1, 2]\): \[ f(x) = 3x^2 + 12x - 1 \] - For the interval \((2, 3]\): \[ f(x) = 37 - x \] ### Step 2: Differentiate the function We need to find the derivative \(f'(x)\) to determine where the function is increasing or decreasing. 1. For the interval \([-1, 2]\): \[ f'(x) = \frac{d}{dx}(3x^2 + 12x - 1) = 6x + 12 \] 2. For the interval \((2, 3]\): \[ f'(x) = \frac{d}{dx}(37 - x) = -1 \] ### Step 3: Analyze the derivative in the intervals 1. **Interval \([-1, 2]\)**: - We check the sign of \(f'(x) = 6x + 12\). - At \(x = -1\): \[ f'(-1) = 6(-1) + 12 = 6 \quad (\text{positive}) \] - At \(x = 2\): \[ f'(2) = 6(2) + 12 = 24 \quad (\text{positive}) \] - Since \(f'(x)\) is positive for all \(x\) in \([-1, 2]\), the function is increasing in this interval. 2. **Interval \((2, 3]\)**: - Here, \(f'(x) = -1\) which is negative. - This indicates that the function is decreasing in the interval \((2, 3]\). ### Step 4: Conclusion Based on the analysis: 1. The function \(f(x)\) is **increasing** in the interval \([-1, 2]\). 2. The function \(f(x)\) is **decreasing** in the interval \((2, 3]\). Thus, both statements provided in the question are correct. ### Final Answer Both statements are correct.
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