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    • Thread Starter
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    Hi guys,

    Would anyone of you know how to solve:

    xy=2
    y=x+1

    and...

    xy=-4
    2y=x+6

    Thanks
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    Substitute one into another ie:

    xy = 2 \text{ and } y=x+1 \Rightarrow x(x+1) = 2
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    ok so far I have:

    x(x+1)
    x^2+x=2

    What is the next stage?
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    Solve the quadratic?
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    That's a quadratic equation... you learn to do them at the age of 12.
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    (Original post by Sophie Maywood)
    xy=2
    y=x+1
    Sub (y=x+1) into the first equation i.e.

    x (x + 1) = 2
    x^2 + x = 2
    X^2 + x - 2 = 0 (then solve as a quadratic)

    (Original post by Sophie Maywood)
    and...

    xy=-4
    2y=x+6
    xy = -4
    therefore 2xy = -8 (2yx = -8)

    sub in the second equation i.e.

    x(x + 6) = -8
    x^2 + 6x = -8
    x^2 + 6x + 8 = 0 (and solve as a quadratic)

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    Ok but on the second equation, how did you obtain the -8
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    (Original post by Sophie Maywood)
    Ok but on the second equation, how did you obtain the -8
    xy = -4

    multiply both sides by 2

    2 x (xy) = 2xy

    2 x -4 = -8
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    i just looked at your profile (OP) and i cannot believe that you wouldnt know how to do this

    your not a troll by any chance are you? :p:
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    no- this is the only part of maths where I get stuck- anyway what's a troll?
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    (Original post by Sophie Maywood)
    no- this is the only part of maths where I get stuck- anyway what's a troll?
    yeah but this is unbelievably easy (as in the only thing easier than this is just addition and multiplication - and subtraction and division lol)

    a troll is generally someone who posts really gay stuff/starts pointless threads just with the intent of annoying people (which im sure youre not )
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    (Original post by Sophie Maywood)
    no- this is the only part of maths where I get stuck
    You're a further maths student, and cannot solve a simple quadratic equation? That's a bit hard to believe, but whatever :p:
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    (Original post by tomthecool)
    You're a further maths student, and cannot solve a simple quadratic equation? That's a bit hard to believe, but whatever :p:
    Not so hard to believe actually. Earlier this week I was teaching Mechanics 1 to a UK born-and-bred Year 12 mathematician with a string of A* GCSE grades (including maths and english).

    The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

    "So what do you do when you meet a door that has PUSH written on it?"

    "I try both things. It works out OK half the time."
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    (Original post by Mr M)
    Not so hard to believe actually. Earlier this week I was teaching Mechanics 1 to a UK born-and-bred Year 12 mathematician with a string of A* GCSE grades (including maths and english).

    The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

    "So what do you do when you meet a door that has PUSH written on it?"

    "I try both things. It works out OK half the time."
    That sounds like a sarcastic joke mate (by your student- not you lol)
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    (Original post by Mr M)
    The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

    "So what do you do when you meet a door that has PUSH written on it?"

    "I try both things. It works out OK half the time."
    :rofl:

    I admit I often don't understand obvious concepts in mechanics even when it's not technical terminology but the above is just hilarious.
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    (Original post by Mr M)
    Not so hard to believe actually. Earlier this week I was teaching Mechanics 1 to a UK born-and-bred Year 12 mathematician with a string of A* GCSE grades (including maths and english).

    The conversation went like this. "I can't do this question because I don't know the difference between push and pull. I know what they mean but I don't know which one is which."

    "So what do you do when you meet a door that has PUSH written on it?"

    "I try both things. It works out OK half the time."
    Yes, that sounds very believable :rolleyes:
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    (Original post by Adhavan)
    That sounds like a sarcastic joke mate (by your student- not you lol)
    Sadly not. The rest of the class were already aware of his little "problem".
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    (Original post by Mr M)
    Sadly not. The rest of the class were already aware of his little "problem".
    maybe they were in on the joke too :p:
 
 
 
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