C1 Quadratics help!

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    I know what to do however all the calculations i've done so far have turned out incorrect,

    for A) ive done 144 - 4 (k + 1 ) (k - 4) > =0 however after expanding the brackets for (k + 1) ( k - 4 ) everything goes wrong

    help please
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    (Original post by melisss22)
    Name:  HELP.PNG
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    I know what to do however all the calculations i've done so far have turned out incorrect,

    for A) ive done 144 - 4 (k + 1 ) (k - 4) > =0 however after expanding the brackets for (k + 1) ( k - 4 ) everything goes wrong

    help please
    Show your expansion, please.
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    Maybe you're making mistakes with the signs? Eg. forgetting that - - = +?

    The other common error that I can think of is that you maybe forgot that the inequality switches when you multiply/divide by -1?

    eg: -a >= -3
    a <= 3
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    (Original post by RDKGames)
    Show your expansion, please.
    144 - 4 ( k^2 - 4k + k - 4 )

    then i did 144 - 4k ^ 2 + 16k - 4k + 16 > = 0
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    (Original post by surina16)
    Maybe you're making mistakes with the signs? Eg. forgetting that - - = +?
    aaaaa i dont think i did ???
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    (Original post by melisss22)
    144 - 4 ( k^2 - 4k + k - 4 )

    then i did 144 - 4k ^ 2 + 16k - 4k + 16 > = 0
    That's good. What's wrong with it then??
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    (Original post by melisss22)
    144 - 4 ( k^2 - 4k + k - 4 )

    then i did 144 - 4k ^ 2 + 16k - 4k + 16 > = 0
    I'd recommend dividing everything by 4 outside of the brackets in the first step shown here before you do anything. It should help you get to the right solution easier.
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    (Original post by melisss22)
    144 - 4 ( k^2 - 4k + k - 4 )

    then i did 144 - 4k ^ 2 + 16k - 4k + 16 > = 0
    144 - 4k ^ 2 + 16k - 4k + 16 > = 0

    160 - 4k ^ 2 + 12k > = 0

    4k^2 -12k -160 =0
    Divide everything by 4 then
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    (Original post by RDKGames)
    That's good. What's wrong with it then??
    oh my god im so stupid igjdosidjfs i just realised i've been simplifying the it wrong the whole time
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    (Original post by melisss22)
    oh my god im so stupid igjdosidjfs i just realised i've been simplifying the it wrong the whole time
    Rookie mistake.
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    (Original post by Ayaz789)
    144 - 4k ^ 2 + 16k - 4k + 16 > = 0

    160 - 4k ^ 2 + 12k > = 0

    4k^2 -12k -160 =0
    Divide everything by 4 then
    i realised i divided 160 / 4 wrong the whole time D: thank you
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    (Original post by melisss22)
    oh my god im so stupid igjdosidjfs i just realised i've been simplifying the it wrong the whole time
    How have you done it wrongg? ^
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    (Original post by melisss22)
    i realised i divided 160 / 4 wrong the whole time D: thank you
    Ahh okay np
 
 
 
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