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CUET · MATHS · PYQ PAPER 2023

Two positive numbers \(x\) and \(y\) such that \(x+y=60\) and \(x y^3\) is maximum are :

  1. A \(x=30, y=30\)
  2. B \(x=20, y=40\)
  3. C \(x=15, y=45\)
  4. D \(x=55, y=5\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(x=15, y=45\)

Step-by-step Solution

Detailed explanation

\(f(y) = (60-y)y^3 = 60y^3 - y^4\) \(f'(y) = 180y^2 - 4y^3 = 0\) \(4y^2(45-y) = 0 \Rightarrow y = 45\) \(x = 60 - 45 = 15\) \(x=15, y=45\)
From CUET
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