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Consider the function f(x)={{:(x^(2),"...

Consider the function
`f(x)={{:(x^(2),"for "xgt2),(3x-2,"for "xle2):}`
which one of the following statements is correct in respect of the following function?

A

f(x) is derivable but not continuous at x = 2

B

f(x) is continuous but not derivable at x = 2

C

f(x) is neither continuous nor derivable at x = 2

D

f(x) is continuous as well as derivable at x = 2

Text Solution

AI Generated Solution

The correct Answer is:
To analyze the function \( f(x) \) given by: \[ f(x) = \begin{cases} x^2 & \text{for } x > 2 \\ 3x - 2 & \text{for } x \leq 2 \end{cases} \] we need to check its continuity and differentiability at the point \( x = 2 \). ### Step 1: Check Continuity at \( x = 2 \) To check if the function is continuous at \( x = 2 \), we need to find the left-hand limit (LHL), right-hand limit (RHL), and the value of the function at that point. 1. **Left-hand limit (LHL)** as \( x \) approaches 2: \[ \text{LHL} = \lim_{x \to 2^-} f(x) = f(2) = 3(2) - 2 = 6 - 2 = 4 \] 2. **Right-hand limit (RHL)** as \( x \) approaches 2: \[ \text{RHL} = \lim_{x \to 2^+} f(x) = 2^2 = 4 \] 3. **Value of the function at \( x = 2 \)**: \[ f(2) = 3(2) - 2 = 4 \] Since LHL = RHL = \( f(2) = 4 \), the function is continuous at \( x = 2 \). ### Step 2: Check Differentiability at \( x = 2 \) To check if the function is differentiable at \( x = 2 \), we need to find the left-hand derivative (LHD) and the right-hand derivative (RHD). 1. **Left-hand derivative (LHD)**: The derivative of \( f(x) = 3x - 2 \) for \( x \leq 2 \) is: \[ f'(x) = 3 \] Thus, \[ \text{LHD} = \lim_{h \to 0^-} \frac{f(2 + h) - f(2)}{h} = 3 \] 2. **Right-hand derivative (RHD)**: The derivative of \( f(x) = x^2 \) for \( x > 2 \) is: \[ f'(x) = 2x \] Thus, \[ \text{RHD} = \lim_{h \to 0^+} \frac{f(2 + h) - f(2)}{h} = \lim_{h \to 0^+} \frac{(2 + h)^2 - 4}{h} = \lim_{h \to 0^+} \frac{4 + 4h + h^2 - 4}{h} = \lim_{h \to 0^+} \frac{4h + h^2}{h} = 4 \] Since LHD = 3 and RHD = 4, they are not equal. Therefore, the function is not differentiable at \( x = 2 \). ### Conclusion The function \( f(x) \) is continuous at \( x = 2 \) but not differentiable at \( x = 2 \). Thus, the correct statement is: **Option B**: \( f(x) \) is continuous but not differentiable at \( x = 2 \). ---
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