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Integrate the rational function: 5x(x+1)(x2-4)

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Question

Integrate the rational function:

`(5x)/((x + 1)(x^2 - 4))`

Sum
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Solution

`(5x)/((x + 1)(x^2 - 4))`

`= 5/((x + 1)(x + 2)(x - 2))`

`(5x)/((x + 1)(x^2 - 4)) => A/(x + 1) + B/(x + 2) + C/(x - 2)`

⇒ 5x = A(x2 - 4) + B (x + 1)(x - 2) + C(x + 1)(x + 2)

Put x = -1

-5 = -3A + 0 = 0

⇒ A `= 5/3`

Put x = -2

-10 = 0 + B(-1)(-4) + 0

⇒ B `= (-5)/2`

Put x = 2

10 = 0 + 0 + 12C

⇒ C `= 5/6`

`therefore int (5x)/((x + 1)(x^2 - 4)`

`= 5/3 int 1/(x + 1)  dx - 5/2 int 1/(x + 1)  dx + 5/6 int 1/(x - 2)  dx`

`= 5/3  log abs (x + 1) - 5/2  log abs (x + 1) + 5/6  log abs (x - 2) + C`

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Chapter 7: Integrals - Exercise 7.5 [Page 322]

APPEARS IN

NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 7 Integrals
Exercise 7.5 | Q 11 | Page 322

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