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JEE Mains · Maths · STD 12 - 6. Application of derivatives

यदि फलन \(f( x )=9 x ^{4}+12 x ^{3}-36 x ^{2}+25\), \(x \in R\), के स्थानीय निम्नतम तथा स्थानीय उच्चतम बिन्दुओं के समुच्चय क्रमशः \(S_{1}\) तथा \(S_{2}\) है, तो 

  1. A \({S_1} = \left\{ { - 2,1} \right\};{S_2} = \left\{ 0 \right\}\)
  2. B \({S_1} = \left\{ { - 2,0} \right\};{S_2} = \left\{ 1 \right\}\)
  3. C \({S_1} = \left\{ { - 2} \right\};{S_2} = \left\{ {0,1} \right\}\)
  4. D \({S_1} = \left\{ { - 1} \right\};{S_2} = \left\{ {0,2} \right\}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \({S_1} = \left\{ { - 2,1} \right\};{S_2} = \left\{ 0 \right\}\)

Step-by-step Solution

Detailed explanation

\(f(x)=9 x^{4}+12 x^{3}-36 x^{2}+25\) \(f(x)=36 x^{3}+36 x^{2}-72 x\) \(=36 x\left(x^{2}+x-2\right)\) \(=36 x(x-1)(x+2)\) Point of minima \(=\{-2,1\}=\mathrm{S}_{1}\) Point of maxima \(=\{0\}=\mathrm{S}_{2}\)
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