syms A B C D E x
R = solve(A*x^4 + B*x^3 + C*x^2 + D*x^1 + E*x^0, x, 'maxdegree', 4);
now use coeffs on your original expression to extract the expression a matching degree 4, b degree 3, and so on. Then
RR = subs(R, [A, B, C, D, E], [a, b, c, d, e]) ;
These will be long and it is very likely that they will be incomprehensible. If someone were to present the same expressions but with any 3 signs changed you would probably never notice or have any idea what the difference meant physically.
