Question:

The set of all the points at which \[ f(x)=|2-|x|| \] is continuous but not differentiable is:

Show Hint

For modulus functions: \[ |g(x)| \] check:

• where \(g(x)=0\),

• where \(g(x)\) is itself non-differentiable.
Those are the possible points of non-differentiability.
Updated On: Oct 5, 2026
  • \(\{0,1,2\}\)
  • \(\{-1,0,2\}\)
  • \(\{-2,0,2\}\)
  • \(\{-2,1,2\}\)
Show Solution
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The Correct Option is C

Solution and Explanation

Concept: Absolute value functions are continuous everywhere but may fail to be differentiable where the expression inside modulus changes sign. For: \[ |g(x)| \] non-differentiability occurs at points where: \[ g(x)=0 \] or where \(g(x)\) itself is non-differentiable.

Step 1: Analyze the given function carefully.
Given: \[ f(x)=|2-|x|| \] We first examine the inner modulus: \[ |x| \] which is not differentiable at: \[ x=0 \] Next consider: \[ 2-|x| \] This becomes zero when: \[ 2-|x|=0 \] \[ |x|=2 \] Thus, \[ x=\pm2 \] At these points, the outer modulus changes sign.

Step 2: Determine differentiability.
The function is continuous everywhere because modulus functions are continuous. However:

• At \(x=0\), \(|x|\) is non-differentiable.

• At \(x=2\) and \(x=-2\), the outer modulus introduces sharp corners.
Hence the function is not differentiable at: \[ x=-2,\;0,\;2 \] Therefore the required set is: \[ \boxed{\{-2,0,2\}} \]
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