Question:

The function \( f(x) = (x^2 - 1)|x^2 - 3x + 2| + \cos|x| \) is non-differentiable at

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If modulus is multiplied by zero at a point, cusp may vanish — check carefully.
Updated On: Apr 23, 2026
  • \( -1 \)
  • \( 0 \)
  • \( 1 \)
  • \( 2 \)
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The Correct Option is D

Solution and Explanation

Concept: Non-differentiability occurs where modulus argument is zero or function is non-smooth.

Step 1:
Solve inside modulus. \[ x^2 - 3x + 2 = 0 \Rightarrow x = 1, 2 \]

Step 2:
Check smoothness: At \( x = 1 \): \[ (x^2 - 1) = 0 \Rightarrow \text{smooth} \] At \( x = 2 \): \[ (x^2 - 1) \neq 0 \Rightarrow \text{kink exists} \]

Step 3:
\( \cos|x| \) is differentiable everywhere except possibly at 0, but it is smooth at 0. Final Answer: \[ x = 2 \]
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