2x^2+ax+8=0 , find possible values for a ?

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    2x^2+ax+8=0 , find possible values for a ? I'm struggling to visualize the data.
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    Try completing the square to get something in the form 2(x+b)^2+c
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    (Original post by nafisaR)
    2x^2+ax+8=0 , find possible values for a ? I'm struggling to visualize the data.
    Uh, under what conditions...? If you don't impose any conditions, then a can be anything...
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    (Original post by nafisaR)
    2x^2+ax+8=0 , find possible values for a ? I'm struggling to visualize the data.
    Assuming that the question states that there are one or more real solutions, or you can assume that's what they mean because of the maths you have been studying, then you could use the discriminant.

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    (Original post by Zacken)
    Uh, under what conditions...? If you don't impose any conditions, then a can be anything...
    You basically have a curve of y=2X^2, with a translation on both axes. To have at least one real solution, you need it to touch / cross the x axis.

    To visualise what you have, draw y=2X^2, then y=2X^2+c and, finally, y=2(x+b)^2+c.

    What is the minimum value of y for the equation y=2X^2+c? For the curve to touch / dip below the x axis, what condition must be satisfied?
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    (Original post by RogerOxon)
    You basically have a curve of y=2X^2, with a translation on both axes. To have at least one real solution, you need it to touch / cross the x axis.

    To visualise what you have, draw y=2X^2, then y=2X^2+c and, finally, y=2(x+b)^2+c.

    What is the minimum value of y for the equation y=2X^2+c? For the curve to touch / dip below the x axis, what condition must be satisfied?
    Is this in reply to the OP's comment : "I'm struggling to visualize the data."?

    It should be said though that using the discriminant here is the standard/quickest approach for this question.

    And did you intend to quote Zacken ? His comment was related to the fact that the OP hadn't given the whole question e.g. the question should have said that the quadratic has real roots (I'm guessing this was the actual question).
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    (Original post by notnek)
    Is this in reply to the OP's comment : "I'm struggling to visualize the data."?
    Yes,

    (Original post by notnek)
    It should be said though that using the discriminant here is the standard/quickest approach for this question.
    Yes, but it is important to understand what this represents on the graph.

    (Original post by notnek)
    And did you intend to quote Zacken ? His comment was related to the fact that the OP hadn't given the whole question e.g. the question should have said that the quadratic has real roots (I'm guessing this was the actual question).
    That was my assumption too.
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    (Original post by RogerOxon)
    You basically have a curve of y=2X^2, with a translation on both axes. To have at least one real solution, you need it to touch / cross the x axis.

    To visualise what you have, draw y=2X^2, then y=2X^2+c and, finally, y=2(x+b)^2+c.

    What is the minimum value of y for the equation y=2X^2+c? For the curve to touch / dip below the x axis, what condition must be satisfied?
    The question doesn't say the quadratic needs real roots. (not sure why you're quoting me...)
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    (Original post by Zacken)
    (not sure why you're quoting me...)
    My mistake - I misread it as a query from the OP.
 
 
 
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