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

माना \(x\) में एक बहुपद \(f ( x )\) की घात \(6\) है, तथा पद \(x ^{6}\) का गुणांक एक है और \(x =-1\) तथा \(x =1\) इसके चरम बिन्दु हैं। यदि \(\lim _{ x \rightarrow 0} \frac{ f ( x )}{ x ^{3}}=1\), है, तो \(5 \cdot f (2)\) बराबर है

  1. A \(121\)
  2. B \(144\)
  3. C \(169\)
  4. D \(121\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(144\)

Step-by-step Solution

Detailed explanation

Let \(f(x)=x^{6}+a x^{5}+b x^{4}+c x^{3}+d x^{2}+e x+f\) as \(\lim _{x \rightarrow 0} \frac{f(x)}{x^{3}}=1\) non-zero finite So, \(d=e=f=0\) and \(f(x)=x^{3}\left(x^{3}+a x^{2}+b x+c\right)\) Hence, \(\lim _{x \rightarrow 0} \frac{ f ( x )}{ x ^{3}}= c =1\) Now, as…
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