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#1 2005-11-28 12:38:04

username
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ln solve for x

solve for x

3ln(-3x+5) = -9

#2 2005-11-28 12:48:28

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: ln solve for x

3ln(-3x+5) = -9

Using alnb = lnb^a : ln(-3x+5)³ = -9

Raise to the power of e: (-3x+5)³ = e^-9

Cube root: -3x+5 = e^-3

Solve: -3x = e^-3 - 5
x = -(e^-3 - 5)/3


Why did the vector cross the road?
It wanted to be normal.

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#3 2005-11-29 11:02:50

irspow
Member
Registered: 2005-11-24
Posts: 455

Re: ln solve for x

I came up with the same answer, but was a little puzzled at mathsyperson's approach.  I am always amazed at the different approaches individuals will take.  I did it like this.

     3ln(-3x+5) = -9     divide by 3

     ln(-3x+5) = -3       raise to e

     -3x+5 = e^-3        subtract 5

     -3x = e^-3 - 5       divide by -3

      x = (e^-3 - 5) / -3

Last edited by irspow (2005-11-29 11:03:22)

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