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Integrate the rational function: 3x+5x3-x2-x+1

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प्रश्न

Integrate the rational function:

`(3x + 5)/(x^3 - x^2 - x + 1)`

योग
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उत्तर

Let `(3x + 5)/(x^3 - x^2 - x + 1)`

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

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

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

`(3x + 5)/((x + 1)(x - 1)^2) = A/(x + 1) = B/(x - 1) + C/((x - 1)^2)`

3x + 5 = A(x - 1)2 + B(x2 - 1) + C(x + 1)       ... (i)

Put x = 1

8 = 0 + 0 + 2C

⇒ C = 4

Put x = -1 

2 = A(-2)2 + 0 = 0

⇒ A = `-1/2`

On comparing the coefficients of x2

0 = A + B

⇒ A = -A `= 1/2`

Hence,  `(3x + 5)/(x^3 - x^2 - x + 1)`

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

On integrating,

`int (3x + 5)/(x^3 - x^2 - x + 1)`

`= -1/2 int 1/(x + 1)  dx + 1/2 int 1/(x - 1)  dx + 4 int 1/((x - 1)^2)  dx`

`= -1/2  log abs (x + 1) + 1/2  log (x - 1) + 4 (1/((x - 1))) + C`

`= 1/2   log abs ((x + 1)/(x - 1)) - 4/((x - 1)) + C`

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अध्याय 7: Integrals - Exercise 7.5 [पृष्ठ ३२२]

APPEARS IN

एनसीईआरटी Mathematics Part 1 and 2 [English] Class 12
अध्याय 7 Integrals
Exercise 7.5 | Q 9 | पृष्ठ ३२२

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