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CUET · MATHS · PYQ PAPER 2025

If \(a, b, c\) are positive real numbers, then the least value of \((a+b+c)(a b+b c+c a)\) is :

  1. A 1
  2. B abc
  3. C 9abc
  4. D 3abc
Verified Solution

Answer & Solution

Correct Answer

(C) 9abc

Step-by-step Solution

Detailed explanation

\(a+b+c \ge 3\sqrt[3]{abc}\) \(ab+bc+ca \ge 3\sqrt[3]{a^2b^2c^2} = 3(abc)^{2/3}\) \((a+b+c)(ab+bc+ca) \ge (3\sqrt[3]{abc})(3(abc)^{2/3}) = 9abc\)