Quick Algebra Ques

Discussion in 'Community Discussion' started by rdf8585, Jul 13, 2006.

  1. rdf8585 macrumors regular

    Joined:
    Feb 15, 2006
    #1
    I need to find the value of the exponential function y=2.50(3.50)^1.4x when x is = 2

    Does that mean y=2.50(3.50)^1.42

    or

    y=2.50(3.50)^1.4(2)

    ???
     
  2. EricNau Moderator emeritus

    EricNau

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    Apr 27, 2005
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    San Francisco, CA
  3. pknz macrumors 68020

    pknz

    Joined:
    Mar 22, 2005
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    NZ
    #3
    <_<

    >_>

    I did not read this then run away. Ummm my battery died?

    Edit: Actually thats not hard at all, I believe EricNau is correct
     
  4. Doctor Q Administrator

    Doctor Q

    Staff Member

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    Los Angeles
    #4
    Google doesn't interpret it right unless you parenthesize properly:

     
  5. savar macrumors 68000

    savar

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    District of Columbia
    #5
    Huh?

    2.50(3.50)^1.4(2)

    Order of operations is ^ before *

    I think Google knows algebra :D
     
  6. rdf8585 thread starter macrumors regular

    Joined:
    Feb 15, 2006
    #6
    3. Solve this exponential equation for x: e^5x= 1 over e^2x+7

    4. Solve this exponential equation for x: 2^4x-7=32

    are these answers right?

    3...... -1
    4....... no idea........
     
  7. Doctor Q Administrator

    Doctor Q

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    #7
    I disagree. Look at the original problem: y=2.50(3.50)^1.4x. I don't think that's intended to be 2.50 * (3.50 ^ 1.4) * x. I think the product 1.4x is to be treated as the exponent, i.e., 2.50 * ( 3.50 ^ ( 1.4 * x ) ). But if you change x to a constant value, 2.50(3.50)^1.4(2), Google doesn't handle it way rdf8585's problem requires.

    In other words, I would interpret 2 ^ 3 * 4 as (2^3)*4, as Google does, but I would interpret 2 ^ 3x as 2 ^ (3 * x) because with the juxtaposition implying implicit multiplication. So my point is that you have to add more parens to get the right answer from Google.
     
  8. Bobdude161 macrumors 65816

    Bobdude161

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    Mar 12, 2006
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    N'Albany, Indiana
    #8
    I wouldn't be using Google all that much to calculate my Algebra problems. I used to have Maple and that piece of software had so many options to solving any equation you could think of. I would know, I had to take a class that taught how to use the software, barely passed it. :eek:
     
  9. pknz macrumors 68020

    pknz

    Joined:
    Mar 22, 2005
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    NZ
    #9
    Asking a mathematical question on MR is guaranteed to start a quarrel.

    Its odd that Maths is so 'opinionated.'
     
  10. Doctor Q Administrator

    Doctor Q

    Staff Member

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    Location:
    Los Angeles
    #10
    It's my fault we're talking about math. I meant the discussion to be about teaching errors, but since my examples were about math, and I can't resist talking about math, I'll have to take the blame. :( :)
     
  11. Atlasland macrumors 6502

    Joined:
    Aug 20, 2005
    Location:
    London, UK
    #11
    3) x = -1

    4) x = 3
     

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