Get the first move right and the rest follows

Martin Hansen

 
To solve the following equation :

 
First multiply through by 4a :

 
Complete the square within the square brackets :

 

 
Square-root both sides :

 
And the well-known formula is there for the taking. 
 

M500 : The Open University's mathematics magazine.
September 2008

Staff INSET presentation at Shrewsbury School.
November 2009

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