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Math Help - Equations

  1. #1
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    Equations

    This is the question:
    'This is what a pupil wrote:
    For all numbers t and w,

    1 + 1 + 2
    t w t+w P.S : the t is supposed to be under the 1, and the w under the 2nd 1, and the t+w under the 2

    Explain why the pupil was wrong'

    Help would be very grateful
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by dravid2 View Post
    This is the question:
    'This is what a pupil wrote:
    For all numbers t and w,

    1 + 1 + 2
    t w t+w P.S : the t is supposed to be under the 1, and the w under the 2nd 1, and the t+w under the 2

    Explain why the pupil was wrong'

    Help would be very grateful
    you did not give the full equation. there is nothing to be wrong about if you just make the claim \frac 1t +  \frac 1w  + \frac 2{t + w}
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  3. #3
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    well, thats what the question says, but instead of 'explain why the pupil is worng it is actually show why the pupil was wrong, does that help u anymore?
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  4. #4
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    Quote Originally Posted by dravid2 View Post
    well, thats what the question says, but instead of 'explain why the pupil is worng it is actually show why the pupil was wrong, does that help u anymore?
    the question is incomplete. you need an equation, you do not have one here. i'm pretty sure you meant to type \frac 1t + \frac 1w = \frac 2{t + w}
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  5. #5
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    oh yes sorry m8, now can u work it out
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  6. #6
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    Quote Originally Posted by dravid2 View Post
    oh yes sorry m8, now can u work it out
    well, the plan here is simple. start with the left hand side and combine the fractions and show that you get something different from the right hand side. can you do that? how would you combine the fractions? what's the first step?
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  7. #7
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    i dont have a clue, dyu just add the numbers and the letters up?
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  8. #8
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    You can do it as Jhevon says or you can also say "if t or w is equal to zero then the expression is undefined". But I think this is not exactly the proof you're looking for.
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    Quote Originally Posted by evrimfeyyaz View Post
    You can do it as Jhevon says or you can also say "if t or w is equal to zero then the expression is undefined". But I think this is not exactly the proof you're looking for.
    in that case, both sides would not make sense, so no.

    another option is to pick values for t and w. say t = 2 and w = 3. plug those into the left hand side, you should get a different answer from when you plug them into the right hand side
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  10. #10
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    what dyu mean they wouldn't make sense, and how dyu combine fractions, and plz could u reply to my topic about simultaneous equations
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  11. #11
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    Quote Originally Posted by dravid2 View Post
    what dyu mean they wouldn't make sense, and how dyu combine fractions, and plz could u reply to my topic about simultaneous equations
    i was saying t or w cannot be zero, since that would mean we divide by zero and that makes no sense.

    the pupil is wrong because:

    \frac 1t + \frac 1w = \frac {t + w}{tw} \ne \frac 2{t + w}
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  12. #12
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    So would this be right:

    The pupil is not right because if you replace t with 2 and w 3 the equation does not work, so therefore he is wrong as the pupil stated that the equation was for all numbers t and w

    Would that be correct?
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    Quote Originally Posted by dravid2 View Post
    So would this be right:

    The pupil is not right because if you replace t with 2 and w 3 the equation does not work, so therefore he is wrong as the pupil stated that the equation was for all numbers t and w

    Would that be correct?
    that's ok i guess. but the last way i suggested shows off that you can add fractions (you'd be surprised how many people can't)
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  14. #14
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    Well, can u give me an example then of like adding 2 fractions together, based on the question?
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  15. #15
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    Quote Originally Posted by dravid2 View Post
    Well, can u give me an example then of like adding 2 fractions together, based on the question?
    i did that in post #11


    This is my 48th post!!!! (and such a dry one at that)
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