function P2_01A
clear, clc, format short g, format compact
xguess = 0.7 ; 
disp('Variable values at the initial estimate');
disp([' Unknown value ' num2str(xguess) '   Function Value ' num2str(NLEfun(xguess))]); 
xsolv=fzero(@NLEfun,xguess); 
disp(' Variable values at the solution');
disp([' Unknown value ' num2str(xsolv) '   Function Value ' num2str(NLEfun(xsolv))]); 
%- - - - - - - - - - - - - - - - - - - - - -
function fV = NLEfun(V); 
P = 56; 
R = .08206; 
T = 450; 
Tc = 405.5; 
Pc = 111.3; 
Pr = P / Pc; 
a = 27 * R ^ 2 * Tc ^ 2 / Pc / 64; 
b = R * Tc / (8 * Pc); 
Z = P * V / (R * T); 
fV = (P + a / (V ^ 2)) * (V - b) - (R * T);