Definitely solved Indefinite Integral!

Calculus Level 4

x ( 5 4 x x 2 ) 3 2 d x = 5 2 x η 5 μ x x 2 + C \large\ \int { \frac { x }{ { ( 5 - 4x - { x }^{ 2 } ) }^{ \frac { 3 }{ 2 } } } \, dx } = \frac { 5 - 2x }{ \eta \sqrt { 5 - \mu x - { x }^{ 2 } } } + C

Find the sum of constants μ + η \mu + \eta .


Clarification: C C denotes the arbitrary constant of integration .


The answer is 13.

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1 solution

Priyanshu Mishra
Aug 28, 2017

Here is the solution

x ( 5 4 x x 2 ) d x = x ( 9 ( x + 2 ) 2 ) d x \large\ \int { \frac { x }{ \left( 5 - 4x - { x }^{ 2 } \right) } dx } = \int { \frac { x }{ \left( 9 - { \left( x + 2 \right) }^{ 2 } \right) } dx } .

Now substitute

( x + 2 ) = 3 sin θ \left( x + 2 \right) = 3\sin { \theta } , to get

x ( 5 4 x x 2 ) d x = x ( 9 ( x + 2 ) 2 ) d x = ( 3 sin θ 2 ) ( 3 cos θ ) 2 d θ = tan θ sec θ 3 d θ 2 9 sec 2 θ d θ = sec θ 3 2 9 tan θ + C \large\ \begin{aligned} \int { \frac { x }{ \left( 5 - 4x - { x }^{ 2 } \right) } dx } = \int { \frac { x }{ \left( 9 - { \left( x + 2 \right) }^{ 2 } \right) } dx } = \int { \frac { \left( 3\sin { \theta } - 2 \right) }{ { \left( 3\cos { \theta } \right) }^{ 2 } } d\theta } = \int { \frac { \tan { \theta } \sec { \theta } }{ 3 } d\theta } - \int { \frac { 2 }{ 9 } \sec ^{ 2 }{ \theta } d\theta } = \frac { \sec { \theta } }{ 3 } - \frac { 2 }{ 9 } \tan { \theta } + C \end{aligned} .

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