2.20 Partial fractions

AQA Edexcel OCR A OCR B (MEI)
A single fraction with linear factors in the denominator can be split into two or more fractions, known as partial fractions

There are three types:

  • \(\dfrac{px+q}{(x+a)(x+b)}=\dfrac{A}{x+a}+\dfrac{B}{x+b}\)

  • \(\dfrac{px^2+qx+r}{(x+a)(x+b)(x+c)}=\dfrac{A}{x+a}+\dfrac{B}{x+b}+\dfrac{C}{x+c}\)

  • \(\dfrac{px^2+qx+r}{(x+a)(x+b)^2}=\dfrac{A}{x+a}+\dfrac{B}{x+b}+\dfrac{C}{(x+b)^2}\)

The constants \(A\), \(B\) and \(C\) can be found by either substitution or equating coefficients.

Partial fractions are used for integration and binomial expansions.
Important
There are three types of partial fractions:

  • \(\dfrac{px+q}{(x+a)(x+b)}=\dfrac{A}{x+a}+\dfrac{B}{x+b}\)

  • \(\dfrac{px^2+qx+r}{(x+a)(x+b)(x+c)}=\dfrac{A}{x+a}+\dfrac{B}{x+b}+\dfrac{C}{x+c}\)

  • \(\dfrac{px^2+qx+r}{(x+a)(x+b)^2}=\dfrac{A}{x+a}+\dfrac{B}{x+b}+\dfrac{C}{(x+b)^2}\)
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