You are using the Symbolic Toolbox in R2014a. Somewhere around release R2015b, the solve() function was upgraded and is now better able to handle nonlinear equations.
The known methods to be able to install MATLAB for free are:
- become a student or faculty at a recognized degree-granting institution that provides access to Total Access Headcount licenses
- become a student of faculty at a secondary school or highschool, which has access to licenses similar to the Total Access Headcount licenses
- become an intern or staff member at Mathworks
- win a Mathworks contest
- write a proposal for writing a textbook that features MATLAB, and submit it to the Mathworks Author Program
- take over complete control of an existing company that has MATLAB licenses. This can be a bit tricky, as finalizing a contract such as that usually requires an "exchange of consideration". Traditionally that involved paying at least $1 for the company, which would be in violation of your requirement that the license be free (rather than reasonably priced.) However, legally speaking, "consideration" does not need to be monetary; you could, for example, sketch a caricature and offer to trade it for control of the company. Note that for this method of obtaining a license to be permitted, you must take on all liabilities of the company involved as well as all assets; you cannot just buy a used MATLAB license from a company at a liquidation sale.