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A2 C3 - do you only take the positive square root? watch

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    I had this question in the june 2014 C3 paper, and as you can see from the answers, the only answer if the positive root (X=5), and doesn't acknowledge any second answer of X, as you would get from the negative root/factoring (would be X=-1)

    So do you only take the positive root from now on? (In as it always seemed to be both)

    Thanks
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    (Original post by JohnnyDavidson)
    I had this question in the june 2014 C3 paper, and as you can see from the answers, the only answer if the positive root (X=5), and doesn't acknowledge any second answer of X, as you would get from the negative root/factoring (would be X=-1)

    So do you only take the positive root from now on? (In as it always seemed to be both)

    Thanks
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Views: 94
Size:  94.2 KBAttachment 508683508685
    yes it looks like you'd use the positive root in this case as i assume the X=-1 solution wouldn't comply with the respective domain (and range) of the initial function (where x>2)
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    (Original post by JohnnyDavidson)
    I had this question in the june 2014 C3 paper, and as you can see from the answers, the only answer if the positive root (X=5), and doesn't acknowledge any second answer of X, as you would get from the negative root/factoring (would be X=-1)

    So do you only take the positive root from now on? (In as it always seemed to be both)

    Thanks
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Size:  94.2 KBAttachment 508683508685
    IT is given in the question that x > 2


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    (Original post by JohnnyDavidson)
    I had this question in the june 2014 C3 paper, and as you can see from the answers, the only answer if the positive root (X=5), and doesn't acknowledge any second answer of X, as you would get from the negative root/factoring (would be X=-1)

    So do you only take the positive root from now on? (In as it always seemed to be both)

    Thanks
    Name:  image.jpeg
Views: 94
Size:  94.2 KBAttachment 508683508685

    http://www.thestudentroom.co.uk/forumdisplay.php?f=38
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    (Original post by xs4)
    yes it looks like you'd use the positive root in this case as i assume the X=-1 solution wouldn't comply with the respective domain (and range) of the initial function (where x>2)
    Ah ok thanks, didnt think to check back to the initial function.

    So in general still take positive and negative, unless mentioned otherwise?
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    (Original post by JohnnyDavidson)
    Ah ok thanks, didnt think to check back to the initial function.

    So in general still take positive and negative, unless mentioned otherwise?
    Yeah
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    (Original post by JohnnyDavidson)
    Ah ok thanks, didnt think to check back to the initial function.

    So in general still take positive and negative, unless mentioned otherwise?
    In general just give the answer to what the domain says

    Pretty sure you could loose marks if you don't? Unless the markscheme says "ignore X=..."
 
 
 
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