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CUET · MATHS · PYQ PAPER 2025

The function \(f(x)=x^3+3 x^2+4 x+4, x \in R\) (set of real numbers):

  1. A is increasing on R
  2. B is decreasing on R
  3. C is decreasing on \((-\infty, 0)\)
  4. D is neither increasing nor decreasing on \((0, \infty)\)
Verified Solution

Answer & Solution

Correct Answer

(A) is increasing on R

Step-by-step Solution

Detailed explanation

\(f'(x) = \frac{d}{dx}(x^3+3 x^2+4 x+4) = 3x^2 + 6x + 4\) \(\Delta = b^2 - 4ac = (6)^2 - 4(3)(4) = 36 - 48 = -12\) Since \(a=3 > 0\) and \(\Delta 0\) for all \(x \in R\). Therefore, \(f(x)\) is increasing on R.