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    How to Solve Quadratic Equations in the Form ax2 + bx + c = 0 with Trinomial factorisation
    By Connor Davidson | July 18th 2009 01:21 PM | Print | E-mail | Track Comments
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    In this short post I wish to explain how to solve simple quadratic equations with Trinomial factorisation

    To solve a quadratic equation in this form there are two main methods you can use to solve these either trinomial (also known as quadratic) factorisation or the quadratic formula. In this article I will explain the factorisation method.

    In maths it is always easier to use an example than to explain with words alone.

    Ex1: Solve by factorisation x2 + 8x + 12 = 0


    1.
      
    Break into two brackets with an x in each:



    > (x ) (x     )


    2.    Find two numbers that add to give 8 and multiply to give 12. Then place in the other side of each bracket.   


    > (x    6) (x    2)



    3.    Put in the sign (+ of -) since the numbers are +ve use a plus sign.




    > (x   +    6) (x   + 2)

    4.    Multiply out to check:



      > (x   +    6) (x   + 2)


    = x2 x 8x + 12

    5.    Re write as:


    > (x   +    6) =0

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    > (x   + 2) = 0


    This gets more complicated when you use either –ve numbers or start with more than one x2. Here is a worked example:




    Ex2: Solve by factorisation 3x2 + x – 4



    >(3x   ) (x   )



    > (2x 4) (x 1)



    > (2x   +    4) (x    -   1)





     





     





     





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