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Integrate the rational function: x(x-1)2(x+2)

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Question

Integrate the rational function:

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

Sum
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Solution

Let `x/((x - 1)^2(x + 2))`

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

⇒ x = A(x - 1)(x + 2) + B(x + 2) + C(x - 1)2   ...(1)

Put x = 1 

1 = 3B

⇒ B = `1/3`

Put x = -2 

-2 = C (-2 - 1)2

⇒ C = `(-2)/9`

On comparing the coefficients of x2

A = `-C = 2/9`

Hence,  `int x/((x+ 1)^2(x - 2))` dx

`= int 2/ (9 (x - 1)) dx + int 1/ (3 (x - 1)^2) dx - int 2/ (9(x + 2)) dx`

`= 2/9  log abs (x - 1) + 1/3 int (x - 1)^-1/-1 - 2/9  log abs (x + 2) + C`

`= 2/9  log abs ((x - 1)/(x + 2)) - 1/(3(x + 1)) + 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 8 | Page 322

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