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    (Original post by lolman42)
    subbing the equation of the line into the circle I get

    7x^2 + 60x + 90 = 0

    what do I do from here?
    You must have realised that was wrong when you could not do part (a)
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    (Original post by Indeterminate)
    Surely, as it's saying "write down", it's asking for

    y=\sqrt{10}
    I think you have mis-read or mis-understood the question
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    (Original post by TenOfThem)
    You must have realised that was wrong when you could not do part (a)
    okay i am not too sure now

    is the expansion 10x^2 + 60x + 100 = 10 ?

    i did b^2-4ac but it does not equal
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    FORGET ALL WHAT i WROTE THERE!! i HAVE GOT IT NOW. what do I do for b now?
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    (Original post by lolman42)
    okay i am not too sure now

    is the expansion 10x^2 + 60x + 100 = 10 ?

    i did b^2-4ac but it does not equal
    0

    FORGET ALL WHAT i WROTE THERE!! i HAVE GOT IT NOW. what do I do for b now?

    So

    You know know the point rom (a) so, sketch and use symmetry
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    (Original post by TenOfThem)
    So

    You know know the point rom (a) so, sketch and use symmetry
    I still do not now the point

    do I solve 10x^2 + 60x +90 =0 to find it?
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    (Original post by lolman42)
    I still do not now the point

    do I solve 10x^2 + 60x +90 =0 to find it?
    yes

    I suggest that you divide by 10 and use the fact that there is only one solution to spot the obvious factorisation
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    (Original post by TenOfThem)
    yes

    I suggest that you divide by 10 and use the fact that there is only one solution to spot the obvious factorisation
    okay so x= -3
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    (Original post by lolman42)
    okay so x= -3
    Sketch and symmetry
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    TenOfThem's method is basically to find the intersection of the two curves, and show that there is only one intersection, so the line must be a tangent to the circle (think, if it crossed the circle there would have to be two solutions, one where it goes into the circle and one where it exits it).
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    (Original post by TenOfThem)
    Sketch and symmetry
    sorry, I am going to have to sound really silly here.

    But I am lost
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    (Original post by lolman42)
    sorry, I am going to have to sound really silly here.

    But I am lost
    Have you sketched?
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    (Original post by TenOfThem)
    Have you sketched?
    I am not exactly sure what I am meant to be sketching
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    (Original post by lolman42)
    I am not exactly sure what I am meant to be sketching
    A circle

    x^2 + y^2 = 10

    and a line

    y = 3x + 10
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    (Original post by TenOfThem)
    A circle

    x^2 + y^2 = 10

    and a line

    y = 3x + 10
    yep, I already had that drawn
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    (Original post by lolman42)
    yep, I already had that drawn
    So you have a circle

    Then you have a line from (0,10) down to (-3,1)

    As I say, symmetry will show you the other line
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    (Original post by TenOfThem)
    So you have a circle

    Then you have a line from (0,10) down to (-3,1)

    As I say, symmetry will show you the other line
    I can't see the symmetry..
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    (Original post by TenOfThem)
    So you have a circle

    Then you have a line from (0,10) down to (-3,1)

    As I say, symmetry will show you the other line
    surely there can only be one line passing through 0,10?
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    Name:  Using For Working Out Stuff P129.png
Views: 21
Size:  60.2 KB

    (Original post by lolman42)
    surely there can only be one line passing through 0,10?
    Well, infinite lines will pass through (0,10)

    But there are 2 that pass through there and are tangents to the circle

    I cannot work out why you cannot see it
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    (Original post by TenOfThem)
    Name:  Using For Working Out Stuff P129.png
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    Well, infinite lines will pass through (0,10)

    ohhh i was doing something different, so the coordinates at the new point of contact are 3,1?

    But there are 2 that pass through there and are tangents to the circle

    I cannot work out why you cannot see it
    ohhh i was doing something different, so the coordinates at the new point of contact are 3,1?
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    (Original post by lolman42)
    ohhh i was doing something different,
    I am intrigued
 
 
 
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