Answer from solver includes new variable z2

We use some equations to calculate the an initial pressure in an air chamber. Three equations that should not lead to redundancy.

Code:

 syms P_air_initi
 V_air_init = ((100000*V_airchamber^1.4)/P_air_initi)^(1/1.4);
 x_airfront_init = V_air_init/A_airchamber;

 eq6 = P_air_initi  -(100000 + rho*g*(H_delivery-(H_airchamber-x_airfront_init))) ==0;
 [sol] = solve(eq6,P_air_initi)

 x_init = x_airfront_init;              % Initial x in the air chamber
 P_init = sol;                              % Initial pressure in air chamber
 V_init = V_air_init;                              % Initial volume air in air chamber

Answer: sol =

(266194982560382061*pi + 1077543584708841800*z2)/(1099511627776*pi)

How do we get to the right solution? Thanks in advance for your effort, A