# Logarithm Equation

• November 6th 2009, 07:07 PM
thebristolsound
Logarithm Equation
• November 6th 2009, 07:17 PM
Defunkt
Quote:

Originally Posted by thebristolsound

Use the fact that $ln(a) - ln(b) = ln(\frac{a}{b})$

And: $e^{ln(a)} = a$

To find the solution.
• November 6th 2009, 07:20 PM
Debsta
Recall the rule lnA - lnB =ln(A/B). Apply that to LHS.
Then you'll have ln [(x+1)/(x-2)} = ln x
Drop the lns so that (x+1)/(x-2)=x
This becomes x+1 = x(x-2) which gives a quadratic and go from there.

Remember to check your answers from the quadratic in the ORIGINAL log equation. Reject answers which don't give pos values for x+1, x-2 or x as ln A is not defined for non-positive A valus.