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JEE Mains · Maths · STD 12 - 13. probability

पूर्णांक \(a \in[-5,30]\) चुनने की प्रायिकता, जबकि \(x ^{2}+2( a +4) x -5 a +64>0, \forall x \in R\) है

  1. A \(\frac{1}{4}\)
  2. B \(\frac{7}{36}\)
  3. C \(\frac{2}{9}\)
  4. D \(\frac{1}{6}\)
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Answer & Solution

Correct Answer

(C) \(\frac{2}{9}\)

Step-by-step Solution

Detailed explanation

\(\mathrm{D}<0\) \(\Rightarrow 4(a+4)^{2}-4(-5 a+64)<0\) \(\Rightarrow a^{2}+16+8 a+5 a-64<0\) \(\Rightarrow a^{2}+13 a-48<0\) \(\Rightarrow(a+16)(a-3)<0\) \(\Rightarrow a \in(-16,3)\) \(\therefore\) Possible a : \(\{-5,-4, \ldots, 2\}\) \(\therefore\) Required probability…
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