You'd have to use the ProductLog function, or Lambert's W function, as it's also called. Here's the solution for you.
This is really part of a Dynamics problem, but I'm running into a purely algebraic problem:
How on earth do you manually solve for k?? Nothing I learned in pre-uni would be able to solve this. Solutions tell you to 'guess and check' ...
You'd have to use the ProductLog function, or Lambert's W function, as it's also called. Here's the solution for you.