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  1. #1
    BeaverTerror Yan's Avatar
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    Can you solve this math problem?

    I can't figure this out and I feel stupid. Help me out here:

    Multiple choice, no calculator allowed:

    If [2^x]-[2^(x-2)]=3(2^13), what is the value of x?

    a) 9
    b) 11
    c) 13
    d) 15
    e) 17

    The answer is d, but how do you solve this without a calculator?

    edit: Nevermind, got it.
    Last edited by Yan; 04-18-10 at 08:32 AM.
    Yan

    2013 True North custom touring; 2010 Novara Randonee; 2009 Unicycle.com Club 24"; 1989 Miele Tivoli; 1979 Colnago Sport

  2. #2
    Hey guyz? Guyz? Wait up!! Siu Blue Wind's Avatar
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    f) 42
    Quote Originally Posted by Buddha
    We are what we think. All that we are arises with our thoughts. With our thoughts, we make the world.
    Quote Originally Posted by making View Post
    Please dont outsmart the censor. That is a very expensive censor and every time one of you guys outsmart it it makes someone at the home office feel bad. We dont wanna do that. So dont cleverly disguise bad words.

  3. #3
    You Know!? For Kids! jsharr's Avatar
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    I try not to put a value on x. Last time I did, he thought it was a bounty and he turned himself into me. I thought he would never leave, and it cost $75 bucks.
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    Quote Originally Posted by colorider View Post
    Phobias are for irrational fears. Fear of junk ripping badgers is perfectly rational. Those things are nasty.

  4. #4
    la vache fantôme phantomcow2's Avatar
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    Usually when your variable (x) is a in exponent form, you take the natural log of both sides. Recall (hopefully) the handy power of logs:

    If you take the log of a^x, where a is a constant, the x goes in front. This results in x(ln(a)). Take the logs of both sides and you'll probably find ln(2) cancels or something.
    C://dos
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    run.dos.run

  5. #5
    la vache fantôme phantomcow2's Avatar
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    Oh, didn't see your edit. Glad you solved it.
    C://dos
    C://dos.run
    run.dos.run

  6. #6
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    Quote Originally Posted by Yan View Post
    I can't figure this out and I feel stupid. Help me out here:

    Multiple choice, no calculator allowed:

    If [2^x]-[2^(x-2)]=3(2^13), what is the value of x?

    a) 9
    b) 11
    c) 13
    d) 15
    e) 17

    The answer is d, but how do you solve this without a calculator?

    edit: Nevermind, got it.
    3(2^13) is (0.75*2*2)*2^13. That is 0.75*2^15. Easy stuff. 2^(x-2) is going to be 1/4 the value of 2^x right. So 3/4 of 2^x equals 3/4 of 2^15. Guess what x equals.

  7. #7
    Senior Member Snicklefritz's Avatar
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    Where did you find this question?

  8. #8
    先輩 Gilla Gorilla's Avatar
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    here's another question for you: Whats the integral of 2xdx between 10 and 13?
    =P
    Last edited by Gilla Gorilla; 04-18-10 at 08:16 PM. Reason: i guess this forum doesn't like calculus....

  9. #9
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    Quote Originally Posted by gilla gorilla View Post
    here's another question for you: Whats the integral of 2xdx between 10 and 13?
    =p
    69.
    Ha
    ha
    ha.

  10. #10
    la vache fantôme phantomcow2's Avatar
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    Quote Originally Posted by recon455 View Post
    69.
    Ha
    ha
    ha.
    no credit without work:
    F(x) = x^2
    F(b) - F(a) = 169-100=69
    C://dos
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    run.dos.run

  11. #11
    Senior Member alexvpaq's Avatar
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    I prefer chemistry class GO PV=nRT!

  12. #12
    RacingBear UmneyDurak's Avatar
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    Quote Originally Posted by Gilla Gorilla View Post
    here's another question for you: Whats the integral of 2xdx between 10 and 13?
    =P
    I used to remember how to do that.
    I see hills.... Bring them on!!!
    Stay calm and bring a towel.

  13. #13
    Senior Member
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    math is the devil.

  14. #14
    Senior Member deraltekluge's Avatar
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    Young man, in mathematics you don't understand things. You just get used to them.
    ~John von Neumann~

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