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Integrate the rational function: 2x-3(x2-1)(2x+3)

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Question

Integrate the rational function:

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

Sum
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Solution

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

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

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

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

Putting x = 1 in equation (1),

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

⇒ -1 = A (2) (5)

⇒ A `= -1/10`

Putting x = -1 in equation (1),

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

⇒ -5 = B (-2)(1)

⇒ B `= 5/2`

Putting `x = -3/2` in equation (1),

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

⇒ -6 = C `(-5/2)(-1/2)`

⇒ C =`- 6 xx 4/5 = -24/5`

`therefore (2x - 3)/((x^2 - 1)(2x + 3)) = - 1/(10(x - 1)) + 5/(2(x + 1)) - 24/(5(2x + 3))`

`therefore int (2x - 3)/((x^2 - 1)(2x+ 3))  dx = -1/10 int 1/(x - 1)  dx + 5/2 int 1/(x + 1)  dx -24/5 int 1/(2x + 3)  dx`

` = - 1/10  log (x - 1) + 5/2  log (x + 1) - 24/5  log ((2x + 3)/2) + C`

`= 5/2  log (x + 1) - 1/10  log (x - 1) - 12/5  log (2x+ 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 10 | Page 322

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