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Integrate the rational function: x(x-1)(x-2)(x-3)

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Question

Integrate the rational function:

`x/((x-1)(x- 2)(x - 3))`

Sum
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Solution

Let `x/((x - 1)(x - 2)(x - 3))`

`= A/(x - 1) + B/(x - 2) + C/(x - 3)`

⇒ x = A(x - 2) (x - 3) + B(x - 1) (x - 3) + C(x - 1) (x - 2)      …(1)

Putting x = 1 in (i), we get

1 = A(1 - 2) (1 - 3)

⇒ A = `1/2`

Putting x = 2 in (i), we get

2 = B (2 - 1) (2 - 3)

⇒ B = - 2

Putting x = 3 in (i), we get

3 = C(3 - 1) (3 - 2)

⇒ C = `3/2`

`therefore x/((x - 1)(x - 2)(x - 3))`

`= 1/(2(x - 1)) - 2/(x - 2) + 3/(2(x - 3))`

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

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

`= 1/2  log (x - 1) - 2  log (x - 2) + 3/2  log (x - 3) + 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 4 | Page 322

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