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\(\frac{5m}{18m^2-18m}-\frac{4}{m+5}\)

 Nov 5, 2018
 #1
avatar+98172 
+2

     5m                           4

___________     -      ___

18m^2 - 18               m + 5

 

Cross-multiply with the same sign as between the fraction

5m (m + 5)  - 4(18m^2 - 18)  =

5m^2 + 25m - 72m^2 + 72 =

-67m^2 + 25m  + 72

 

Product of the denominators

(18m^2 - 18)  ( m + 5)  =

18m^3 - 18m + 5m^2- 80

18m^3 + 5m^2 - 18m - 80

 

Note, RP...if your teacher wants you to factor 18m^2 - 18 first,we have

18 (m^2 - 1)  =  18 (m + 1) (m - 1)

 

So...the product of the denominators is

18 ( m + 1) (m - 1) (m + 5)

 

 

So...the final answer is

 

-67m^2 + 25m + 72

__________________

18 ( m + 1) ( m - 1) ( m + 5)

 

 

 

cool cool cool

 Nov 5, 2018

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