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    I was doing the June 2013 AQA C1 paper and I'm stuck on question 7a), I work it out as b^2 - 4ac > 0 for real roots however they answer wants the > to have a line underneath it, I reverse the symbol and get the answer however, I do not know when / why I need to put a line under the <.

    I have attached the question and mark scheme thanks

    Btw my working is:
    real roots when b^2 - 4ac > 0
    [-(k-2)]^2 - 4 x (2k-7) x (k-3) > 0
    (-k+2)^2 - (8k+28)(k-3) > 0
    k^2 - 4k +4 - (8k^2 - 24k - 28k + 84) > 0
    k^2 - 4k + 4 -8k^2 + 52k - 84 >0
    -7k^2 + 48k -80 >0
    7k^2 - 48k +80 < 0
    therefore shown
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    You can also have a single real, repeated root when the discriminant is 0
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    (Original post by Sayless)
    real roots when b^2 - 4ac > 0
    If the discriminant is:
    &gt;0 then the roots are real and distinct - i.e. two of them.
    =0 then there is one real root (repeated).
    &lt;0 there are two complex roots.

    So, if you require the roots to be real, then the discriminant must be positive or it must be zero.

    b^2-4ac\geq 0
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    (Original post by ghostwalker)
    If the discriminant is:
    &gt;0 then the roots are real and distinct - i.e. two of them.
    =0 then there is one real root (repeated).
    &lt;0 there are two complex roots.

    So, if you require the roots to be real, then the discriminant must be positive or it must be zero.

    b^2-4ac\geq 0
    So only real roots at = 0 and >0 and > with a line underneath means both of = and > therefore thats why it was used, thanks for the help
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    (Original post by Sayless)
    So only real roots at = 0 and >0 and > with a line underneath means both of = and > therefore thats why it was used, thanks for the help
    Just to be clear > with a line underneath is read as "greater than or equal to"
 
 
 
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