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Let f(x)={(-,1, -2lexlt0),(x^2,-1,0lexlt...

Let `f(x)={(-,1, -2lexlt0),(x^2,-1,0lexlt2):}` if `g(x)=|f(x)|+f(|x|)` then `g(x)` in `(-2,2)` is
(A) not continuous is (B) not differential at one point (C) differential at all points (D) not differential at two points

A

Differentiable at all points

B

not differentiable at two points

C

Not continuous

D

not differentiable at one point

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the function \( f(x) \) and then compute \( g(x) \) based on the given definitions. ### Step-by-Step Solution: 1. **Define the function \( f(x) \)**: \[ f(x) = \begin{cases} -1 & \text{if } -2 \leq x < 0 \\ x^2 - 1 & \text{if } 0 \leq x < 2 \end{cases} \] 2. **Calculate \( |f(x)| \)**: - For \( -2 \leq x < 0 \): \( f(x) = -1 \) implies \( |f(x)| = 1 \). - For \( 0 \leq x < 2 \): \( f(x) = x^2 - 1 \) implies \( |f(x)| = x^2 - 1 \) when \( x^2 - 1 \geq 0 \) (which is for \( x \geq 1 \)) and \( |f(x)| = 1 - x^2 \) when \( x < 1 \). Thus, we can summarize: \[ |f(x)| = \begin{cases} 1 & \text{if } -2 \leq x < 0 \\ 1 - x^2 & \text{if } 0 \leq x < 1 \\ x^2 - 1 & \text{if } 1 \leq x < 2 \end{cases} \] 3. **Calculate \( f(|x|) \)**: - For \( -2 \leq x < 0 \): \( |x| = -x \) which is in the range \( [0, 2) \), so \( f(|x|) = f(-x) = -1 \). - For \( 0 \leq x < 2 \): \( f(|x|) = f(x) = x^2 - 1 \). Thus, we can summarize: \[ f(|x|) = \begin{cases} -1 & \text{if } -2 \leq x < 0 \\ x^2 - 1 & \text{if } 0 \leq x < 2 \end{cases} \] 4. **Define \( g(x) = |f(x)| + f(|x|) \)**: - For \( -2 \leq x < 0 \): \[ g(x) = 1 + (-1) = 0 \] - For \( 0 \leq x < 1 \): \[ g(x) = (1 - x^2) + (x^2 - 1) = 0 \] - For \( 1 \leq x < 2 \): \[ g(x) = (x^2 - 1) + (x^2 - 1) = 2x^2 - 2 \] Thus, we can summarize: \[ g(x) = \begin{cases} 0 & \text{if } -2 \leq x < 1 \\ 2x^2 - 2 & \text{if } 1 \leq x < 2 \end{cases} \] 5. **Check continuity of \( g(x) \)**: - At \( x = 0 \): \( g(0^-) = 0 \) and \( g(0^+) = 0 \) ⇒ Continuous. - At \( x = 1 \): \( g(1^-) = 0 \) and \( g(1^+) = 0 \) ⇒ Continuous. 6. **Check differentiability of \( g(x) \)**: - For \( -2 < x < 0 \): \( g'(x) = 0 \). - For \( 0 < x < 1 \): \( g'(x) = 0 \). - For \( 1 < x < 2 \): \( g'(x) = 4x \). - At \( x = 0 \): - Left-hand derivative: \( 0 \) - Right-hand derivative: \( 0 \) - Thus, \( g(x) \) is differentiable at \( x = 0 \). - At \( x = 1 \): - Left-hand derivative: \( 0 \) - Right-hand derivative: \( 4 \) - Thus, \( g(x) \) is not differentiable at \( x = 1 \). ### Conclusion: The function \( g(x) \) is not differentiable at one point (specifically at \( x = 1 \)). Therefore, the answer is: **(B) not differentiable at one point.**
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