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

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Question

Integrate the rational function:

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

Sum
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Solution

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

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

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

Putting x = 1 in (i), we get

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

⇒ 2 = A(-1) (-2)

⇒ A = 1

Putting x = 2 in (i), we get

6 - 1 = B (2 - 1) (2 - 3)

⇒ 5 = B(1) (-1)

⇒ B = -5

Putting x = 3 in (i), we get

9 - 1 = C (3 - 1) (3 - 2)

⇒ 8 = C (2) (1)

⇒ C = 4

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

`= 1/(x - 1) - 5/(x - 2) + 4/(x - 3)`

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

`= int1/(x - 1)  dx - 5 int 1/(x - 2)  dx + 4 int 1/(x - 3)  dx`

= log (x - 1) - 5 log (x - 2) + 4 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 3 | Page 322

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