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Math Help - Use algebra to find the x and y intercepts , for a quadratic equation

  1. #1
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    Use algebra to find the x and y intercepts , for a quadratic equation

    1. The problem statement, all variables and given/known data

    Use algebra to find the x-intercepts and y-intercept of The graph of y=-x^2/5+x/5+6
    this is a parabola.

    2. Relevant equations
    y=-x^2/5+x/5+6


    3. The attempt at a solution
    Find the y-intercept , which is substitute 0=x into the equation to find the answer , done that .
    The problem I have is where to start to find the x-intercept , I know that y=0 so I now have x^2/5+x/5+6=0 , but believe I can't now factorise this equation and will have to first clear the fractions first . Is this the right place to start.
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  2. #2
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    Re: Use algebra to find the x and y intercepts , for a quadratic equation

    is it y=-x^2/5+x/5+6 or x^2/5+x/5+6=0?,
    btw, for -x^2/5+x/5+6=0, then x^2-x-30=0, x = (1+/- 11)/2, ie x=6 or -5
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  3. #3
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    Re: Use algebra to find the x and y intercepts , for a quadratic equation

    Sorry missed the - sign in front of x^2 in my first reply. Method of course still applies.
    Last edited by biffboy; July 7th 2012 at 02:27 AM.
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    Re: Use algebra to find the x and y intercepts , for a quadratic equation

    The equation is y=-x^2/5+x/5+6 and I'm looking for the x-intercept .
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    Re: Use algebra to find the x and y intercepts , for a quadratic equation

    Quote Originally Posted by duggielanger View Post
    The equation is y=-x^2/5+x/5+6 and I'm looking for the x-intercept .
    Can you solve x^2-x-30=0~? That is all that is needed.
    Last edited by Plato; July 7th 2012 at 05:29 AM.
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  6. #6
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    Re: Use algebra to find the x and y intercepts , for a quadratic equation

    I think I can , I would factorise this equation to get my final answer. which is (x-1)(x+5) I think, and these are my x-intercepts. But to get this part do I simply the fraction by finding the the products of 5 and 6 and then simplify to x^2-x-30=0.
    And sorry one last question, would squaring and or using then quadratic formula get the same answer.
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    Re: Use algebra to find the x and y intercepts , for a quadratic equation

    Quote Originally Posted by duggielanger View Post
    I think I can , I would factorise this equation to get my final answer. which is (x-1)(x+5) I think, and these are my x-intercepts. But to get this part do I simply the fraction by finding the the products of 5 and 6 and then simplify to x^2-x-30=0.
    And sorry one last question, would squaring and or using then quadratic formula get the same answer.
    It factors as (x-6)(x+5). Thus your x-intercepts are (6,0)~\&~(-5,0)(
    Thanks from duggielanger
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  8. #8
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    Re: Use algebra to find the x and y intercepts , for a quadratic equation

    Ok thank you , I will go back and study the section again to get to grips with it.
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