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NCERT Class 12 · Ch 6 Exercise 6.3 · Q14

NCERT Class 12 Maths · Chapter 6 Applications Of Derivatives · Exercise 6.3 Question 14

Find positive x,y with x+y=60 maximizing xy³.

💡 Concept Hints

  1. Identify the domain and the inner and outer functions, or the relevant one-sided limits.
  2. Apply the appropriate differentiation or limit rule, keep all chain factors, and check exceptional points.

✅ Step-by-Step Solution

Final Answer: x=15, y=45.
  1. Use the fixed sum to express the second number in terms of x. The objective is \(x \left(60 - x\right)^{3}\) on (0,60).
  2. Differentiate: \(- 4 \left(x - 60\right)^{2} \left(x - 15\right)\). The feasible interior stationary point is x=15.
  3. The second derivative there is \(-8100\). The objective tends to zero at the positive-domain endpoints and has only this interior maximum.

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