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Tamil Nadu Board of Secondary EducationHSC Commerce Class 11

Resolve into partial fraction for the following: 1x2-1 - Business Mathematics and Statistics

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Question

Resolve into partial fraction for the following:

`1/(x^2 - 1)`

Sum

Solution

Let `1/(x^2 - 1) = 1/((x + 1)(x - 1)) = "A"/(x + 1) + "B"/(x - 1)`    ....(1)

`1/((x + 1)(x - 1)) = ("A"(x - 1) + "B"(x + 1))/((x + 1)(x - 1))`

1 = A(x – 1) + B(x + 1) ……. (2)

Put x = 1 in (2) we get

1 = 0 + B(1 + 1)

1 = B(2)

B = `1/2`

Put x = -1 in (2) we get

1 = A(-1 – 1) + B(-1 + 1)

1 = -2A + 0

A = `(-1)/2`

Using A = `(-1)/2`, B = `1/2` in (1) we get

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

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

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Partial Fractions
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Chapter 2: Algebra - Exercise 2.1 [Page 29]

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