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Let's discuss Mathematics

Discussion in 'Science & Technology' started by ParadigmShifter, Mar 16, 2009.

  1. ParadigmShifter

    ParadigmShifter Random Nonsense Generator

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  2. Mise

    Mise isle of lucy

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    "Whatever you do to one side you must do to the other"?
     
  3. IdiotsOpposite

    IdiotsOpposite Boom, headshot.

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    Partial fraction decomposition is the devil!
     
  4. Quackers

    Quackers The Frog

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    yeah thats what I mean.

    will have a look at the link

    some easy ones I can work out. but stuff like

    express x in terms of y when

    y=x-3/x+2
     
  5. IdiotsOpposite

    IdiotsOpposite Boom, headshot.

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    Multiply both sides by (x+2) to get a linear equation in x. Then solve for x.
     
  6. Quackers

    Quackers The Frog

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    Well does anybody know a place where I can do some exercises? Online?

    I think I just need some practice to get it into ma brain before I start doing moddeling using straight lines....
     
  7. ParadigmShifter

    ParadigmShifter Random Nonsense Generator

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    Shouldn't you be in London rioting anyway Quacko?

    Did you not do A-level maths before starting a degree in economics?

    EDIT: And you should use brackets in your example, do you mean

    y = (x-3) / (x+2)

    or

    y = x - (3/x) + 2

    or something else? The latter is the usual precedence rules for division...
     
  8. IdiotsOpposite

    IdiotsOpposite Boom, headshot.

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    Mathematically speaking, why is there rioting in London?

    Remember to use the words "set", "subset", and "population" in your answer.
     
  9. ParadigmShifter

    ParadigmShifter Random Nonsense Generator

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    Students aren't happy about plans to raise fees to up to £9000. A subset of them are rioting. Some of them set off fire extinguishers. They probably haven't had sets in a long while.
     
  10. IdiotsOpposite

    IdiotsOpposite Boom, headshot.

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    Nice job. I wish I could pity the students, but I'm paying the equivalent of £14730 (according to Wolfram-Alpha), so...
     
  11. ParadigmShifter

    ParadigmShifter Random Nonsense Generator

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  12. IdiotsOpposite

    IdiotsOpposite Boom, headshot.

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  13. Mise

    Mise isle of lucy

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    A-level maths textbook?
     
  14. ParadigmShifter

    ParadigmShifter Random Nonsense Generator

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    Have a gold star then!

     
  15. Atticus

    Atticus Deity Retired Moderator

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    We had to pay equivalent of 83 euros when I begun my studies in 1996, and something like 90 euros when I ended them in 2003. That's how we roll in Librulistan :smug:
     
  16. IdiotsOpposite

    IdiotsOpposite Boom, headshot.

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    ...any chance I can move to Finland?
     
  17. Quackers

    Quackers The Frog

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    I was accepted with just a B in GCSE mathematics (A in exam, c in coursework ;)). I haven't done maths in two years so I need to brush up on just everything tbh.

    I mean the former.
     
  18. sanabas

    sanabas Psycho Bunny Hall of Fame Staff

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    2 ways to do it:

    First, multiply both sides by (x+2)

    xy + 2y = x-3

    Not obvious where to go from there, but remember you're trying to get x by itself. So let's get all the terms with x on one side, all the terms without on the other, by subtracting xy from both sides and adding 3 to both sides.

    2y + 3 = x - xy

    factorise the RHS

    2y + 3 = x (1-y)

    Divide both sides by (1-y)

    x = (2y+3)/(1-y)

    Second way to do it is to do the division (x-3)/(x+2) at the start, or just write x-3 as x+2-5, either of those gives you

    y = 1 - 5/(x+2), which is more straightforward to rearrange:

    y-1 = -5/(x+2)

    x+2 = -5/(y-1)

    x+2 = 5/(1-y)

    x = 5/(1-y) - 2

    x = [5 - 2(1-y)]/(1-y)

    x = (2y+3)/(1-y)


    And yeah, best way to practice is just head for the library and find a textbook of the right level.
     
  19. cyther

    cyther Lord of the Dance

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    So yesterday I was bored after a few hours of not knowing what to do, I started playing with the Riemann Zeta function on Mathematica.

    I really couldn't find anything interesting about that right away (yeah I know about the Riemann hypothesis, I meant more of myself not the function). So I started pressing the ' key to take derivatives. I was bothered by the notation and wanted to show the guy sitting next to me how silly the notation was. That's when I noticed this:

    Zeta''''''(2) was about 720.

    I removed one of the 's and saw that the result I got was about -120.

    So I kept going down to Zeta'(2) and got about 1. I also went up to around 60 and it was still about n! (There was an error of around .001).

    Has anyone seen / can explain the connection between the zeta and n! (or gamma shifted over if you prefer)?

    I figured that what I have is:

    The nth derivative of the Riemann Zeta function evaluated at 2 is about equal to n! * (-1)^n.

    Edit:

    Did some more testing and found out that:

    The nth derivative of the Riemann Zeta function evaluated at 0 is about equal to n! * (-1).
     
  20. Spoonwood

    Spoonwood Grand Philosopher

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    In civ III each scientific tribe gets a free technology (tech) at an era change. Let's say there are 4 techs available for a specific era change (modern age). The probability of drawing any of the particular techs is .25. Say we have 7 tribes that get a free tech at an age change. The probability of all 7 tribes getting one of the same techs is .25^7=.000061, so it's 4*.25^7=.000244 for all 7 tribes getting any of the same techs. What's the probability of 7 tribes getting exactly 2 of the techs? For 7 tribes getting exactly 3 of the techs? For 7 tribes getting exactly 4 of the techs? How does one compute these?
     

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