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Math Help - Parabola question???

  1. #1
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    Unhappy Parabola question???

    My question is kind of basic and stupid... but how in the world do you graph THIS question??
    I need someone to walk me through it.

    y = x^2 - 3x - 4

    Should i factorise it or what?? It seems like iI should know this question but i don't.
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  2. #2
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    Re: Parabola question???

    Factorisation gives y=(x-4)(x+1), thus the roots are x=-1 and x=4. Further the minimum is attained at x=3/2 (half way between the roots) and y(3/2) = -25/4. Now draw a nice parabola through (-1,0) , (3/2,-25/4) and (4,0).
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  3. #3
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    Re: Parabola question???

    Yep that looks right to me. If you have a basic calculator you can put it into table mode, and input the equation. It then gives you the results for any input of x.

    However, it is easy to calculte without a calculator. Just get take values for x, say -5, 0, 5, and stick them into the equation. Work it out, and you will obtain a table of results.

    ie.
    y=x^2-3x-4

    Take x=0

    then, y=0^2-(3\times0)-4
    Therefore, y=-4

    Do the same for the other values, and then you can plot them.
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  4. #4
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    Re: Parabola question???

    hi would I do something similar to solve equations such as

    y=-3x+2

    and

    y=2x^2-7x-4

    dave
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  5. #5
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    Re: Parabola question???

    Then start your own thread. Do not "hijack" someone else's thread to ask separate questions.
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  6. #6
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    Re: Parabola question???

    sorry, I`ll do it now
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