Partial Fraction Decomposition
Solved Problems
Example 7.
Determine a partial fraction decomposition for the function
Solution.
The partial fraction decomposition has the form
We combine the partial fractions on the right side into a single fraction and then equate the numerators on both sides. This yields:
Hence we obtain the following system of equations:
Solving it, we find the unknown coefficients:
The partial fraction decomposition is given by
Example 8.
Determine a partial fraction decomposition for the function
Solution.
First we factor the cubic function in the denominator:
As the denominator contains only linear factors, the decomposition has the form
Combining the partial fractions on the right side into a single fraction and equating the numerators on both sides, we have:
The system of equations for the unknown coefficients is written as
It has the following solution:
so the decomposition of the original rational function is expressed by the equation:
Example 9.
Decompose
Solution.
Given the irreducible quadratic factor
The equation for the unknown coefficients is given by
or
We obtain the system of equations:
This yields:
Hence, the partial fraction decomposition is written as
Example 10.
Expand the rational function
Solution.
Note that the denominator
To determine the unknown coefficients
By equating coefficients of similar powers on both sides, we have
We solve the resulting system and find
Hence, the partial fraction decomposition of the rational function is given by
Example 11.
Decompose
Solution.
The denominator has the irreducible quadratic factor
By equating the numerators on both sides of the equation, we have
We get the following system of equations:
It has the solution
Hence, the partial fraction decomposition is given by