Transform (A-B)*ln(c)+B*ln(d)-A*ln(f) to (A-B)*ln(c/f)+B*ln(d/f)

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Curl
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How can I go from expression 1 to expression 2? Its easy to "show" they are equivalent, but if you started with 1, how will I get to 2? I got no clue how to transform it.



1
[ (A-B)*ln(c)+( B*ln(d)-A*ln(f) ) ] /ln(d/f)

2
(A-B)*ln(c/f)/ln(d/f)+B

I bet it's cake and I'm dumb.
 

Discussion

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Hi Curl! :smile:

Add B*ln(f) - B*ln(f) to the top. :wink:
 
It is possible to show this, although it is not extremely easy.
One thing you do need is that
ln(a) - ln(b) = ln(a / b).

I suggest to start by opening up the "square" brackets.
You can also add 0, in the form (A - B) ln(f) - (A - B) ln(f) = A ln(f) - B ln(f) - (A - B) ln(f).
 
tiny-tim said:
Hi Curl! :smile:

Add B*ln(f) - B*ln(f) to the top. :wink:

haha, so I was right:

I bet it's cake and I'm dumb.