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Thread: old ruse question

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    old ruse question

    ruse-solution.png

    Did they make a mistake on line two, with x(x-a)?? [When I multiplied out, i got x(x+a), ending up with the locus as a circle with centre (-a/2, b/2) instead of (a/2, b/2)]

    also, is there supposed to be a restriction on the locus? like excluding (a,0) (because z =/ a on the denominator)

    Thanks!

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    Junior Member fan96's Avatar
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    Re: old ruse question

    Note the denominator in the first line



    That looks wrong. However they later multiplied by instead, so it seems two mistakes have cancelled out?

    I don't think there are any further restrictions.

    The only conditions given to you are



    and

    Last edited by fan96; 6 Feb 2018 at 5:53 PM.
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    HSC 2018 - [English Adv.] • [Maths Ext. 1] • [Maths Ext. 2] • [Chemistry] • [Software Design and Development]

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    Re: old ruse question



    in the very first line, its works out as
    Last edited by darkk_blu; 6 Feb 2018 at 6:08 PM.
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    Re: old ruse question

    Quote Originally Posted by fan96 View Post
    Note the denominator in the first line



    That looks wrong. However they later multiplied by instead, so it seems two mistakes have cancelled out?

    I don't think there are any further restrictions.

    The only conditions given to you are



    and

    ahh I see it now haha, yeah that confused me for a while.

    so would they give a specific condition for z =/ a for some locus question like


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    Re: old ruse question

    I can't believe that question was also in my 4U test today, but I really shouldn't have been. I stuffed up and put instead, lol, lost a mark.

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    Re: old ruse question

    Quote Originally Posted by darkk_blu View Post
    I can't believe that question was also in my 4U test today, but I really shouldn't have been. I stuffed up and put instead, lol, lost a mark.
    rip, are you from ruse as well?

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    Junior Member fan96's Avatar
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    Re: old ruse question

    Quote Originally Posted by altSwift View Post
    ahh I see it now haha, yeah that confused me for a while.

    so would they give a specific condition for z =/ a for some locus question like

    I'm not sure what you're asking, sorry.
    HSC 2018 - [English Adv.] • [Maths Ext. 1] • [Maths Ext. 2] • [Chemistry] • [Software Design and Development]

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    Re: old ruse question

    Quote Originally Posted by altSwift View Post
    rip, are you from ruse as well?
    Nah, I'm not that smart, btw do you know if people actually get 100 in ext 2 or is that just scaling?

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    Re: old ruse question

    The graph of a locus represents all the possible points that satisfies a given equation.

    You have to exclude (a,0), as it lies on the circle.

    Otherwise, you are saying that z=a satisfies Re(z-ib/z-a)=0, which is false.
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    Re: old ruse question

    Quote Originally Posted by darkk_blu View Post
    Nah, I'm not that smart, btw do you know if people actually get 100 in ext 2 or is that just scaling?
    100 as in raw mark? Apparently Anthony Henderson from USYD got 100% in 93'

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    Re: old ruse question

    Quote Originally Posted by camelrider View Post
    The graph of a locus represents all the possible points that satisfies a given equation.

    You have to exclude (a,0), as it lies on the circle.

    Otherwise, you are saying that z=a satisfies Re(z-ib/z-a)=0, which is false.
    I was thinking this... I wonder why they didn't include it in the answers, thanks!

    Quote Originally Posted by fan96 View Post
    I'm not sure what you're asking, sorry.
    All good, camel just explained it
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