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.Sam.

  • 3 years ago

A problem Solve for x, 7.3^(x-1)+5-3^(x+1)=0

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  1. .Sam.
    • 3 years ago
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    \[\huge 7.3^{x-1}+5-3^{x+1}=0\]

  2. perl
    • 3 years ago
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    is that 7*3^(x-1) or (7.3)^(x-1)

  3. .Sam.
    • 3 years ago
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    decimal

  4. perl
    • 3 years ago
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    hmmm, doesnt look easy

  5. lgbasallote
    • 3 years ago
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    do tell me..does this involve canceling 3^x-1 the solution i thought had that..

  6. Ishaan94
    • 3 years ago
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    \[3^x = \frac{15}{2}\] \[x = \log_3 \frac{15}2\]

  7. .Sam.
    • 3 years ago
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    @Ishaan94 that's true if the decimal was "dot" *

  8. Ishaan94
    • 3 years ago
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    Oh, my bad... so it's \[(7.3)^{x-1} + 5-3^{x+1}=0\]Hmm Now I feel stupid :/

  9. perl
    • 3 years ago
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    ok I have an idea

  10. perl
    • 3 years ago
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    |dw:1333364793236:dw|

  11. perl
    • 3 years ago
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    |dw:1333364860619:dw|

  12. Ishaan94
    • 3 years ago
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    campbell decimal point, 7.3 = 73/10

  13. Ishaan94
    • 3 years ago
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    :/

  14. perl
    • 3 years ago
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    its an annoying problem. whats the bloody solution?

  15. anonymoustwo44
    • 3 years ago
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    ln(a+b) is not the same as lna +lnb

  16. Ishaan94
    • 3 years ago
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    You can't take log like that

  17. Ishaan94
    • 3 years ago
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    I think 7.3 has something to do with 5, we should try to use 5

  18. perl
    • 3 years ago
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    did sam leave,

  19. experimentX
    • 3 years ago
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    wolf's answer http://www.wolframalpha.com/input/?i=7.3%5E%28x-1%29%2B5-3%5E%28x%2B1%29%3D0

  20. perl
    • 3 years ago
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    why did he say this is easy problem

  21. karatechopper
    • 3 years ago
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    hhe says its easy and im still stuck on first step, can i switch signs?

  22. Ishaan94
    • 3 years ago
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    Who is hhe?

  23. karatechopper
    • 3 years ago
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    i meant he, meaning sam

  24. perl
    • 3 years ago
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    i think this could somehow become a quadratic, with the right substitution

  25. perl
    • 3 years ago
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    |dw:1333366072740:dw|

  26. experimentX
    • 3 years ago
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    i don't think general method we use would work

  27. experimentX
    • 3 years ago
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    how do you solve this 2^x - x = 2

  28. anonymoustwo44
    • 3 years ago
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    I think we could only use newtons method......

  29. anonymoustwo44
    • 3 years ago
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    first we approximate an answer....

  30. perl
    • 3 years ago
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    i want an EXACT solution

  31. anonymoustwo44
    • 3 years ago
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    then use the newton's method to get a better aproximation

  32. anonymoustwo44
    • 3 years ago
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    we continue this until we're satisfied

  33. anonymoustwo44
    • 3 years ago
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    but we can't still get the exact though :(

  34. perl
    • 3 years ago
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    summon sam

  35. experimentX
    • 3 years ago
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    currently the best way to solve is graphical method ... lol

  36. anonymoustwo44
    • 3 years ago
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    yeah

  37. anonymoustwo44
    • 3 years ago
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    the number 5 is irritating

  38. perl
    • 3 years ago
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    i sent sam a message, he better respond .

  39. perl
    • 3 years ago
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    what is classic about this problem anyway?

  40. Ishaan94
    • 3 years ago
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    @satellite73

  41. satellite73
    • 3 years ago
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    i assume that is \(7.3^{x-1}\) and not \(7\cdot 3^{x-1}\) so i have no ideas yet

  42. satellite73
    • 3 years ago
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    must be something special about 7.3 that i do not see

  43. perl
    • 3 years ago
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    can you guys tell me later, i gotta sleep

  44. perl
    • 3 years ago
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    ok try this , let u = 3^(x+1)

  45. perl
    • 3 years ago
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    i assume there is an exact solution, otherwise youve wasted my time

  46. .Sam.
    • 3 years ago
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    I can see that you guys think so hard, lol

  47. perl
    • 3 years ago
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    please give us hint

  48. .Sam.
    • 3 years ago
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    Sad thing for you @perl There's no exact solution but approximation \[7.3^{x-1}=3^{x+1}-5\]

  49. Mimi_x3
    • 3 years ago
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    i knew that newtoms method of approximation yesterday..

  50. anonymoustwo44
    • 3 years ago
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    I TOLD YOU SO

  51. Mimi_x3
    • 3 years ago
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    from yesterday*

  52. perl
    • 3 years ago
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    it would be more interesting if there was exact solution , :(

  53. perl
    • 3 years ago
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    i was confused since you said it was easy problem , rats

  54. anonymoustwo44
    • 3 years ago
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    newton's method :D

  55. anonymoustwo44
    • 3 years ago
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    newton's method :D

  56. perl
    • 3 years ago
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    ok then how is it easy to approximate?

  57. .Sam.
    • 3 years ago
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    Its easy you don't even need to think, lol

  58. perl
    • 3 years ago
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    what?

  59. perl
    • 3 years ago
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    it didnt look easy on wolfram

  60. perl
    • 3 years ago
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    sam , so are you going to post the solution or not. cuz im getting really tired

  61. perl
    • 3 years ago
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    you can use a calculator for this. is that your 'easy' solution ?

  62. .Sam.
    • 3 years ago
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    you have to graph it for 7.3^(x-1) and 3^(x+1)-5 pick some points

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  63. perl
    • 3 years ago
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    what program do you use to graph that?

  64. .Sam.
    • 3 years ago
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    its a tedious job though, but if you have a graphing calc, it will be fine

  65. perl
    • 3 years ago
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    then why do you say its easy?

  66. perl
    • 3 years ago
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    http://www.wolframalpha.com/input/?i=7.3^%28x-1%29%2B5-3^%28x%2B1%29%3D0

  67. perl
    • 3 years ago
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    what do you mean , pick some points? estimate

  68. .Sam.
    • 3 years ago
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    yes , estimate

  69. Mimi_x3
    • 3 years ago
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    Newtons Method i think..

  70. perl
    • 3 years ago
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    i dont think so, its just approximation problem

  71. Mimi_x3
    • 3 years ago
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    then what else?

  72. perl
    • 3 years ago
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    anyways, the question seemed pretty ambiguous. i didnt know what they meant by 'easy'

  73. Mimi_x3
    • 3 years ago
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    lol, thats all? guessing?

  74. .Sam.
    • 3 years ago
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    you can use this program to graph https://www.desmos.com/calculator/c

  75. perl
    • 3 years ago
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    then you do screen capture?

  76. Mimi_x3
    • 3 years ago
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    sigh..you can state your question as finding the approximation than 'solve for x'

  77. .Sam.
    • 3 years ago
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    @Mimi_x3 yes its a bit of disappointing, but I'll come up with a new question later :)

  78. .Sam.
    • 3 years ago
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    @perl no i dont screen cap on that software

  79. Mimi_x3
    • 3 years ago
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    lol, i wanted to see a solution..but there is no solution *sigh*

  80. .Sam.
    • 3 years ago
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    the solution is approximation ,lol

  81. Mimi_x3
    • 3 years ago
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    like the working out..

  82. .Sam.
    • 3 years ago
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    Nevermind I'll come up a new one :)

  83. Mimi_x3
    • 3 years ago
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    Alright, please state your question correctly next time.

  84. perl
    • 3 years ago
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    so you copy as a file

  85. perl
    • 3 years ago
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    I think there is a confusion, he copied the problem originally with multiplication 7*3^(x-1)

  86. apoorvk
    • 3 years ago
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    c'mon i got the approximate thing using 'jugaad' :/

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