Machine dynamics with Matlab

Sir, I have doubt in solving this question from an exercise from edx course. It is Working with Symbolic Expressions and Functions, here I need to find the solution and solve the equation.
Question is in the pic.

syms x;    % Define a symbolic variable x     
f(x) = -x^3+x^2-x+5;  % Define the required function 
symEq = solve(f(x))       % Define a suitable equation for the problem
fplot(f,[0,10])                   % Plot the function 
sols = double(symEq)  % Solve the solution
df=diff(f(x))
zero_crossing_complete = double(solve(df==0)) % Get the zero crossings of the equtation
zero_crossing_real = real(zero_crossing_complete)  % Only extract the real zero crossings

The solution is as such,
symEq =
 
 root(z^3 - z^2 + z - 5, z, 1)
 root(z^3 - z^2 + z - 5, z, 2)
 root(z^3 - z^2 + z - 5, z, 3)
 

sols =

  -0.4406 - 1.5696i
  -0.4406 + 1.5696i
   1.8812 + 0.0000i

 
df =
 
- 3*x^2 + 2*x - 1
 

zero_crossing_complete =

   0.3333 - 0.4714i
   0.3333 + 0.4714i


zero_crossing_real =

    0.3333
    0.3333

Answer 1

[Black Woods]

x = sym('x');                              
f(x) = [-x^3+x^2-x+5];                                        
figure('WindowStyle','docked');             
fplot(f(x),[0,10]);                         
axis('square')                              
sols = solve(f(x)==0);                     
zero_crossing_complete = double(sols);      
zero_crossing_real = real(zero_crossing_complete(end,end));