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

Let \(P ( x )\) be a real polynomial of degree \(3\) which vanishes at \(x =-3 .\) Let \(P ( x )\) have local minima at \(x=1,\) local maxima at \(x=-1\) and \(\int_{-1}^{1} P ( x ) d x =18,\) then the sum of all the coefficients of the polynomial \(P ( x )\) is equal to ....... .

  1. A \(16\)
  2. B \(8\)
  3. C \(4\)
  4. D \(12\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(8\)

Step-by-step Solution

Detailed explanation

Let \(p^{\prime}(x)=a(x-1)(x+1)=a\left(x^{2}-1\right)\) \(p ( x )= a \int\left( x ^{2}-1\right) d x + c\) \(=a\left(\frac{x^{3}}{3}-x\right)+c\) Now \(p(-3)=0\) \(\Rightarrow a \left(-\frac{27}{3}+3\right)+ c =0\) \(\Rightarrow-6 a+c=0\) Now…
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