Partial Fractions

 

 

Contents

 

Partial Fractions

 

Linear Factors

 

Repeated Linear Factors

 

Quadratic Factors

 

Improper Fractions

 

Quiz

 

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Improper Fractions
 
 
Express in partial fractions:
                
 
    Notice the numerator is in degree 3 and the denominator is in degree 2.
    Hence this is an improper fraction.
    Improper fractions as such can be expressed as
                     
    There are 2 ways to solve this question.
 
  Method 1:
 
     Let
        
 
     From here, we can tell that A = 1, as coefficient of x3 in numerator, divided by coefficient of x2 in denominator, is 2/2 = 1.
 
    C and D can be found by using "cover-up" rule:
 
           
               = -2
 
           
                = 3
 
    Use algebraic identity to find B:
 
    2x3 - x2 - x + 5 = (x + B) (2x + 1) (x - 2) - 2 (x - 2) + 3 (2x + 1)
 
    Let x = 0,
             -2B + 4 + 3 = 5
                            B = 1
 
Therefore,
        
 
Method 2:  Long division
 
     
 
   Performing long division,
 
     
 
   Using the result,
 
        
        
 
   Using cover-up rule,
 
                 A = [ 4(-0.5) + 7] / (-0.5-2)
                    = -2
                 B = [ 4(2) + 7] / [ 2(2) + 1]
                    = 3
 
   Therefore,