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donovan11

  • 5 years ago

Solve the logarithmic equation for . Please round the answer to four decimal places, if necessary. ln(x-4)+ln(x+5)=1

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  1. donovan11
    • 5 years ago
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    Reason I'm confused is because unlike log, in ln the exponential form is e^y=x and I'm having trouble solving the rest

  2. amistre64
    • 5 years ago
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    ln(a) + ln(b) = ln(ab)

  3. donovan11
    • 5 years ago
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    That's x^2+x-20?

  4. amistre64
    • 5 years ago
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    yep. now, ln(0) = 1 because e^0 = 1

  5. myininaya
    • 5 years ago
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    and also any number to the 0 power except 0 is 1

  6. amistre64
    • 5 years ago
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    your equation is really: x^2 +x - 20 = 0

  7. myininaya
    • 5 years ago
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    wait!

  8. amistre64
    • 5 years ago
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    or (x-4) (x+5) = 0

  9. myininaya
    • 5 years ago
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    e^1=e

  10. myininaya
    • 5 years ago
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    we have (x-4)(x+5)=e

  11. amistre64
    • 5 years ago
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    lol..... maybe it does, and maybe it doesnt :)

  12. beens
    • 5 years ago
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    yes myininaya

  13. myininaya
    • 5 years ago
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    if we do it like amistre we would make the problem much easier but also kindof wrong

  14. myininaya
    • 5 years ago
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    and kindof wrong is just wrong

  15. donovan11
    • 5 years ago
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    now im confused >_<

  16. amistre64
    • 5 years ago
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    horseshoe and handgranades me friend :)

  17. myininaya
    • 5 years ago
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    so we have x^2-9x+20+e=0

  18. myininaya
    • 5 years ago
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    oops -e

  19. donovan11
    • 5 years ago
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    wouldnt it be -e?

  20. myininaya
    • 5 years ago
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    Yes i blame amistre

  21. myininaya
    • 5 years ago
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    lol

  22. beens
    • 5 years ago
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    bring over 1 to the left at the start...before changinglg form...

  23. amistre64
    • 5 years ago
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    ...its my liver pills...blame the liver pills :)

  24. donovan11
    • 5 years ago
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    so whats the answer?

  25. myininaya
    • 5 years ago
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    use quadractic formula x=(9@sqrt(81-4(1)(20-e))/2 where @ means + or -, but make sure your answer is positive because you cannot do ln(negative)

  26. beens
    • 5 years ago
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    sorry...doesn't make a difference what I said

  27. beens
    • 5 years ago
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    Quadratic formula the way to go

  28. donovan11
    • 5 years ago
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    this is what i put on the formula -1+squareroot(1^2 -4(1)(20-e))))/2

  29. myininaya
    • 5 years ago
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    no

  30. myininaya
    • 5 years ago
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    a=1 n=-9 c=20-e correct?

  31. beens
    • 5 years ago
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    c=-20-e

  32. myininaya
    • 5 years ago
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    b=-9*

  33. beens
    • 5 years ago
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    b=1

  34. donovan11
    • 5 years ago
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    no b =1

  35. myininaya
    • 5 years ago
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    dont listen to me

  36. myininaya
    • 5 years ago
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    im doing two things at once sorry

  37. donovan11
    • 5 years ago
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    my calculator wont work

  38. myininaya
    • 5 years ago
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    (-1+sqrt(1-4(-20-e))/2=4.2925 and (-1-sqrt(1-4(-20-e))/2=-5.2925 but we can't use -5.2925 since it is negative and the natural log of a negative number doesnt exist

  39. amistre64
    • 5 years ago
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    x can be negative if it is not the only thing controling the value of the log. the thing is: x-4 needs to be greater than 0 and, x+5 needs to be greater than 0. x >4 serves both cases.

  40. myininaya
    • 5 years ago
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    correct!

  41. myininaya
    • 5 years ago
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    that negative number gives you another negative number when you plug it into x-4

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