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CUET · MATHS · PYQ PAPER 2025

If \(y=(x+1)\left(x^2+1\right)\left(x^4+1\right)\left(x^8+1\right)\) then \(\frac{d y}{d x}\) at \(x = -1\) is

  1. A 8
  2. B -8
  3. C 16
  4. D -16
Verified Solution

Answer & Solution

Correct Answer

(A) 8

Step-by-step Solution

Detailed explanation

\(y=(x+1)f(x)\) where \(f(x) = \left(x^2+1\right)\left(x^4+1\right)\left(x^8+1\right)\) \(\frac{d y}{d x} = 1 \cdot f(x) + (x+1)f'(x)\) At \(x = -1\): \(\left.\frac{d y}{d x}\right|_{x=-1} = f(-1) + (-1+1)f'(-1) = f(-1)\) \(f(-1) = ((-1)^2+1)((-1)^4+1)((-1)^8+1)\)…