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JEE Main 202226 JulyMorning Shift
Exam
JEE Main
Year
2022
Date
26 July
Shift
Morning Shift
Subject
Mathematics
Chapter
Definite Integration

JEE Main 2022 · 26 July · Morning Shift · Mathematics · Definite Integration

If n(2n + 1) ∫ _ 0 ^ 1 (1 - x ^ n ) ^ 2n dx = 1177 ∫ _ 0 ^ 1 (1 - x...

If n(2n+1)∫01(1−xn)2ndx=1177∫01(1−xn)2n+1dxn\left(2n + 1\right){∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n}dx = 1177{∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n + 1}dx, then n∈Nn \in N is equal to _______.

Correct answer

0

Step-by-step solution

Let I1=∫01(1−xn)2ndx{I}_{1} = {∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n}dx and I2=∫01(1−xn)2n+1dx{I}_{2} = {∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n + 1}dx

Now on solving I2{I}_{2} we get,

I2=∫01(1−xn)2n+1⋅1dx{I}_{2} = {∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n + 1} \cdot 1dx

Now on using by parts integration we get,

⇒I2=(1−xn)2n+1.x01−∫01(2n+1)(1−xn)2n(−nxn−1)xdx⇒ {I}_{2} = {\left(1 - {x}^{n}\right)}^{2n + 1} . {x}_{0}^{1} - {∫}_{0}^{1}\left(2n + 1\right){\left(1 - {x}^{n}\right)}^{2n}\left(- n{x}^{n - 1}\right)xdx

⇒I2=−n(2n+1){I2−I1}{asI1=∫01(1−xn)2ndx}⇒ {I}_{2} = - n\left(2n + 1\right)\left\{{I}_{2} - {I}_{1}\right\} \left\{\text{as}{I}_{1} = {∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n}dx\right\}

⇒(2n2+n+1)I2=n(2n+1)I1⇒ \left(2{n}^{2} + n + 1\right){I}_{2} = n\left(2n + 1\right){I}_{1}

\left\{\text{Given}n\left(2n + 1\right){∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n}dx = 1177{∫}_{0}^{1}{\left(1 - {x}^{n}\right)}^{2n + 1}dx\right\}</p><p></p><p>⇒ \dfrac{{I}_{1}}{{I}_{2}} = \dfrac{2{n}^{2} + n + 1}{n\left(2n + 1\right)} = \dfrac{1177}{n\left(2n + 1\right)}</p><p></p><p>⇒ 2{n}^{2} + n - 1176 = 0</p><p></p><p>⇒ n = \dfrac{- 1 \pm \sqrt{1 + 4 \times 2 \times 1176}}{4}</p><p></p><p>⇒ n = \dfrac{- 1 \pm \sqrt{9409}}{4}</p><p></p><p>⇒ n = \dfrac{- 1 \pm 97}{4}</p><p></p><p>⇒ n = 24or\dfrac{- 49}{2}</p><p>Butgiven</p><p>But givenn \in Nsoson = 24

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