Here's the question you clicked on:
Answer should be: http://d.pr/i/lRJn
\[e^{9a} + 2e^{3a} - 3e^{a} = 300\] Let \(e^a=y\) \[y^9+2y^3-3y=300\] \[y^9=300+3y-2y^3\] \[ln(y)^9=ln(300+3y-2y^3)\] \[9ln(y)=ln(300+3y-2y^3)\] \[ln(y)=\frac{1}{9}ln(300+3y-2y^3)\] \[ln(e^a)=\frac{1}{9}ln(300+3e^a-2e^{3a})\] \[a=\frac{1}{9}\ln(300+3e^a-2e^{3a})\]
This is the proving solution, I don't think you can solve for 'a' all at one side.