# MATLAB: What does “z” stands for in “solve” function

rootsolve

Hi everyone, I've been struggling trying to clear f in the next equation using the "solve" function:
syms  f G m Q;eqn = ((f^2)*(m-1))/(sqrt(((m*(f^2)-1)^2)+((f^2)*(((f^2)-1)^2)*((m-1)^2)*(Q^2))))==G;x = solve(eqn,f)
The answer I get is the following:
x =
root(2*G^2*Q^2*m*z^3 - G^2*Q^2*m^2*z^3 - G^2*Q^2*z^3 - 4*G^2*Q^2*m*z^2 + 2*G^2*Q^2*m^2*z^2 + 2*G^2*Q^2*z^2 - G^2*m^2*z^2 - 2*m*z^2 + m^2*z^2 + z^2 + 2*G^2*Q^2*m*z - G^2*Q^2*m^2*z + 2*G^2*m*z - G^2*Q^2*z - G^2, z, 1)^(1/2)root(2*G^2*Q^2*m*z^3 - G^2*Q^2*m^2*z^3 - G^2*Q^2*z^3 - 4*G^2*Q^2*m*z^2 + 2*G^2*Q^2*m^2*z^2 + 2*G^2*Q^2*z^2 - G^2*m^2*z^2 - 2*m*z^2 + m^2*z^2 + z^2 + 2*G^2*Q^2*m*z - G^2*Q^2*m^2*z + 2*G^2*m*z - G^2*Q^2*z - G^2, z, 2)^(1/2)root(2*G^2*Q^2*m*z^3 - G^2*Q^2*m^2*z^3 - G^2*Q^2*z^3 - 4*G^2*Q^2*m*z^2 + 2*G^2*Q^2*m^2*z^2 + 2*G^2*Q^2*z^2 - G^2*m^2*z^2 - 2*m*z^2 + m^2*z^2 + z^2 + 2*G^2*Q^2*m*z - G^2*Q^2*m^2*z + 2*G^2*m*z - G^2*Q^2*z - G^2, z, 3)^(1/2)-root(2*G^2*Q^2*m*z^3 - G^2*Q^2*m^2*z^3 - G^2*Q^2*z^3 - 4*G^2*Q^2*m*z^2 + 2*G^2*Q^2*m^2*z^2 + 2*G^2*Q^2*z^2 - G^2*m^2*z^2 - 2*m*z^2 + m^2*z^2 + z^2 + 2*G^2*Q^2*m*z - G^2*Q^2*m^2*z + 2*G^2*m*z - G^2*Q^2*z - G^2, z, 1)^(1/2)-root(2*G^2*Q^2*m*z^3 - G^2*Q^2*m^2*z^3 - G^2*Q^2*z^3 - 4*G^2*Q^2*m*z^2 + 2*G^2*Q^2*m^2*z^2 + 2*G^2*Q^2*z^2 - G^2*m^2*z^2 - 2*m*z^2 + m^2*z^2 + z^2 + 2*G^2*Q^2*m*z - G^2*Q^2*m^2*z + 2*G^2*m*z - G^2*Q^2*z - G^2, z, 2)^(1/2)-root(2*G^2*Q^2*m*z^3 - G^2*Q^2*m^2*z^3 - G^2*Q^2*z^3 - 4*G^2*Q^2*m*z^2 + 2*G^2*Q^2*m^2*z^2 + 2*G^2*Q^2*z^2 - G^2*m^2*z^2 - 2*m*z^2 + m^2*z^2 + z^2 + 2*G^2*Q^2*m*z - G^2*Q^2*m^2*z + 2*G^2*m*z - G^2*Q^2*z - G^2, z, 3)^(1/2)
But I just don't understand where does the "z" come from or what does it mean. Can anyone please help me out here? Thanks!

root(2*G^2*Q^2*m*z^3 - G^2*Q^2*m^2*z^3 - G^2*Q^2*z^3 - 4*G^2*Q^2*m*z^2 + 2*G^2*Q^2*m^2*z^2 + 2*G^2*Q^2*z^2 - G^2*m^2*z^2 - 2*m*z^2 + m^2*z^2 + z^2 + 2*G^2*Q^2*m*z - G^2*Q^2*m^2*z + 2*G^2*m*z - G^2*Q^2*z - G^2, z, 1)
x = solve(eqn, f, 'MaxDegree', 3)