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Thread: ACT problem

  1. MHB Apprentice

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    #1
    Assume that (x-4) is a factor of 2x^2-4x-z. What is the value of z?

    How would you set it up to use the foil method?

  2. Pessimist Singularitarian
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    #2
    Let:

    $ \displaystyle f(x)=2x^2-4x-z$

    Now, if $x-4$ is a factor of $f$, then we must have:

    $ \displaystyle f(4)=0$

    So, this allows us to write:

    $ \displaystyle 2(4)^2-4(4)-z=0$

    Can you proceed?

  3. MHB Apprentice

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    #3 Thread Author
    Quote Originally Posted by MarkFL View Post
    Let:

    $ \displaystyle f(x)=2x^2-4x-z$

    Now, if $x-4$ is a factor of $f$, then we must have:

    $ \displaystyle f(4)=0$

    So, this allows us to write:

    $ \displaystyle 2(4)^2-4(4)-z=0$

    Can you proceed?
    32-16-z+=0; 16-z=0; 16=z

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