I want to have some algebra expression so that once it is solved the answer becomes $\displaystyle E=mc^2$. I want it to be a little complicated though where the answer isn't obvious and you do actually have to reduces, cancel ect. Something like this for example. I know it doesn't mean anything but to give you an idea, once solved and everything cancels ect the solution is $\displaystyle E=mc^2$

$\displaystyle ac^2+\frac{E^2}{6-m^2} = -6-a \frac{1}{E^2}$

Thanks!