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synthetic division (Definition)

Synthetic division is simply a shorthand for long division, when one of the factors is linear. So when an equation such as

$\displaystyle y = 2x^2 + 10x + 12$
is given and a factor of $ x+3$ is known, we can do the following:
$ \phantom{-3}$   $ 2$ $ 10$ $ 12$
         

First, we can use $ -3$ since $ -3$ is a solution if $ x+3=0$.

$ -3$   $ 2$ $ 10$ $ 12$
         

Carry down the first coefficient:

$ -3$   $ 2$ $ 10$ $ 12$
         
    $ 2$    

Multiply $ 2$ by $ -3$:

$ -3$   $ 2$ $ 10$ $ 12$
      $ -6$  
    $ 2$    

Add up $ 10$ and $ -6$:

$ -3$   $ 2$ $ 10$ $ 12$
      $ -6$  
    $ 2$ $ 4$  

Multiply $ 4$ by $ -3$:

$ -3$   $ 2$ $ 10$ $ 12$
      $ -6$ $ -12$
    $ 2$ $ 4$ 0

This means that, by factoring the equation by $ x+3$, we will get another factor as $ 2x+4$.

Synthetic is simply an variation of the long division -- a version that's manipulated and simplified to shorten the calculations.



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Cross-references: variation, coefficient, solution, equation, factors, long division
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This is version 4 of synthetic division, born on 2004-01-20, modified 2004-03-04.
Object id is 5531, canonical name is SyntheticDivision.
Accessed 8704 times total.

Classification:
AMS MSC12D05 (Field theory and polynomials :: Real and complex fields :: Polynomials: factorization)

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