L lowend New member Joined Feb 4, 2011 Messages 4 Feb 4, 2011 #1 The function is P = 12 + 20ln(x) P = 90 is given so, 90 = 12 + 20ln(x) and they want to solve for x. Logs have always given me problems. I can solve for P if x is given but don't know where to start on this one. Thanks so much! Steve
The function is P = 12 + 20ln(x) P = 90 is given so, 90 = 12 + 20ln(x) and they want to solve for x. Logs have always given me problems. I can solve for P if x is given but don't know where to start on this one. Thanks so much! Steve
S soroban Elite Member Joined Jan 28, 2005 Messages 5,584 Feb 4, 2011 #2 Hello, Steve! \(\displaystyle \text{Given: }\ \,=\, 12 + 20\ln x,\,\text{ and }P = 90\) \(\displaystyle \text{Solve for }x.\) Click to expand... \(\displaystyle \text{We have: }\;12 + 20\ln x \:=\:90 \quad\Rightarrow\quad 20\ln x \:=\:78 \quad\Rightarrow\quad \ln x \,=\,\tfrac{78}{20} \,=\,3.9\) \(\displaystyle \text{Therefore: }\;x \:=\:e^{3.9} \;\approx\;49.4\)
Hello, Steve! \(\displaystyle \text{Given: }\ \,=\, 12 + 20\ln x,\,\text{ and }P = 90\) \(\displaystyle \text{Solve for }x.\) Click to expand... \(\displaystyle \text{We have: }\;12 + 20\ln x \:=\:90 \quad\Rightarrow\quad 20\ln x \:=\:78 \quad\Rightarrow\quad \ln x \,=\,\tfrac{78}{20} \,=\,3.9\) \(\displaystyle \text{Therefore: }\;x \:=\:e^{3.9} \;\approx\;49.4\)
L lowend New member Joined Feb 4, 2011 Messages 4 Feb 5, 2011 #3 Thanks! It's funny how simple problems like this can trip me up. I'm so glad I found this place