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Math Help - can you assist please?

  1. #1
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    can you assist please?

    hi guys can someone assist with this one please before i pull any more hair out.

    the age of a machine,x, in years is related to the probability of breakdown,y, by the formula

    x=3 + ln( y/1-y)

    determine the probability of breakdown for 1,3,10 years!

    i am fairly sure 1st i take away the 3 from both sides thus leaving x-3=ln(y/1-y).

    then inverse of ln makes y/1-y=e^x-3?

    what do you think any help appreciated,logs,powers etc not my strong point!

    ps. hope this is the correct section to be in.




    thankyou
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  2. #2
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    the age of a machine,x, in years is related to the probability of breakdown,y, by the formula

    x=3 + ln( y/1-y)

    determine the probability of breakdown for 1,3,10 years!

    i am fairly sure 1st i take away the 3 from both sides thus leaving x-3=ln(y/1-y).

    then inverse of ln makes y/1-y=e^x-3?
    yes, now multiply both sides by 1-y, and move the ye^x-3 to the left and factorise out the y and then divide both sides by e^x-3

    y= (1-y) (e^x-3)

    y=e^x-3 - y e^x-3

    y + y e^x-3=e^x-3

    y(1 + e^x-3)=e^x-3

    y=e^x-3/(1 + e^x-3)

    now you got y by itself.

    sub in those values of x to get probabilty.

    it seems correct but correct me if im wrong
    Last edited by mr fantastic; November 5th 2009 at 03:11 AM. Reason: Added quote tags.
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  3. #3
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    Smile

    ah of course! how stupid of me.

    i was actually trying to cross multiply which didnt leave y on its own ,many thanks for the very quick reply.
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  4. #4
    Junior Member
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    Quote Originally Posted by ads114 View Post
    ah of course! how stupid of me.

    i was actually trying to cross multiply which didnt leave y on its own ,many thanks for the very quick reply.
    np glad i could help.
    btw theres a thanks button some where
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  5. #5
    MHF Contributor

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    Oddly enough, posts that I, myself, made, don't have a "thank you" button by them! That cuts down on my "thank you"s a lot!
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