Friday 19 June 2015

algebra precalculus - Why is $ln(sqrt{|2x-5|}) + frac{1}{2} ln(|2x+3|) neq ln(sqrt{|2x-5|}) + ln(sqrt{|2x+3|})$ in Wolfram Alpha?



According to Wolfram Alpha, $$\frac{1}{2} \ln(|2x+3|) = \ln(\sqrt{|2x+3|})$$



is always true, which makes sense given what I know of log rules.



However, if I add the expression $\ln(\sqrt{|2x-5|})$ to both sides of that equation, as such: $$\ln(\sqrt{|2x-5|}) + \frac{1}{2} \ln(|2x+3|) = \ln(\sqrt{|2x-5|}) + \ln(\sqrt{|2x+3|})$$



WA tells me that the two sides of this equation are not always equal! How is this possible if $\frac{1}{2} \ln(|2x+3|) = \ln(\sqrt{|2x+3|})$ is always true and I'm adding the same expression to both sides of the equation?
What's going on here?




EDIT: Here's the WA output: enter image description here


Answer



OK I tried it. Now what? Is this different from yours?



WA image


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