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JEE Main 202127 AugustEvening Shift
Exam
JEE Main
Year
2021
Date
27 August
Shift
Evening Shift
Subject
Mathematics
Chapter
Indefinite Integration

JEE Main 2021 · 27 August · Evening Shift · Mathematics · Indefinite Integration

∫ 2 e ^ x + 3 e ^ - x 4 e ^ x + 7 e ^ - x dx = (1)/(14)(ux + v _ e...

∫2ex+3e−x4ex+7e−xdx=114(ux+vlog⁡e(4ex+7e−x))+C∫ \dfrac{2{e}^{x} + 3{e}^{- x}}{4{e}^{x} + 7{e}^{- x}}dx = \dfrac{1}{14}\left(ux + v{\log}_{e}\left(4{e}^{x} + 7{e}^{- x}\right)\right) + C, where CC is a constant of integration, then u+vu + v is equal to

Correct answer

0

Step-by-step solution

I=∫2ex+3e−x4ex+7e−xdx=∫2ex+34e2x+7dxI = ∫ \dfrac{2{e}^{x} + 3{e}^{- x}}{4{e}^{x} + 7{e}^{- x}}dx = ∫ \dfrac{2{e}^{x} + 3}{4{e}^{2x} + 7}dx
Here 2e2x+3=A(8e2x)+B(4e2x+7)2{e}^{2x} + 3 = A\left(8{e}^{2x}\right) + B\left(4{e}^{2x} + 7\right)
⇒2e2x+3=(8A+4B)e2x+7B⇒ 2{e}^{2x} + 3 = ( 8A + 4B ) {e}^{2x} + 7B
⇒B=37 and A=128⇒ B = \dfrac{3}{7} \text{ and } A = \dfrac{1}{28}
I=∫128(8e2x)+37(4e2x+7)4e2x+7dxI = ∫ \dfrac{\dfrac{1}{28}\left(8{e}^{2x}\right) + \dfrac{3}{7}\left(4{e}^{2x} + 7\right)}{4{e}^{2x} + 7}dx
I=128ln⁡∣4e2x+7∣+37x+CI = \dfrac{1}{28}\ln \left|4{e}^{2x} + 7\right| + \dfrac{3}{7}x + C
I=128ln∣ex(4ex+7e−x∣+37x+C)<br/>I = \dfrac{1}{28}ln ∣ {e}^{x}\left(4{e}^{x} + 7{e}^{- x} ∣ + \dfrac{3}{7}x + C\right)<br />⇒ u = \dfrac{13}{2} \text{ and } v = \dfrac{1}{2}<br/><br />⇒ u + v = \dfrac{13}{2} + \dfrac{1}{2} = 7
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