尝试在Matlab中求解二次方程

Question

I have just started to use Matlab and I am struggling to solve quadratic equations. I am studying with the following guide:

A guide to Matlab for beginners and experienced users

Link to a preview.

I tried to solve the equation provided by the book (page 17). Despite typing exactly what the book instructed, I did not get the desired output. Note that firstly I tried with solve command and secondly with fzero but none worked out:

>> clear
>> syms x
>> solve ('x^2 - 2*x - 4 = 0')
Error using solve>getEqns (line 418)
List of equations must not be empty.

Error in solve (line 226)
[eqns,vars,options] = getEqns(varargin{:});

>> fzero ('x^2 - 2*x - 4 = 0')
Error using fzero (line 121)
FZERO requires at least two input arguments or a structure
with valid fields.

I do not understand the correction 'List of equations must not be empty' after using solve command. Besides, when I tried to use fzero command I got 'FZERO requires at least two input arguments or a structure with valid fields' which I did not get the hang of either. I looked for an alternative and I found x could be enclosed in parenthesis:

>> solve ('x^2 - 2*x - 4 = 0', x)
Error using solve>getEqns (line 418)
List of equations must not be empty.

Error in solve (line 226)
[eqns,vars,options] = getEqns(varargin{:});

But again 'List of equations must not be empty' came as a result. Please take into consideration the fact that I am a beginner and I understand this question may be too obvious to you, however I have been trying for a while and could not figure it out.

Thanks

Answer 1

Based on the following link, it looks like specifying your equation as a string (char vector) might be your issue. Equations and systems solver in MATLAB . In your situation, I would try the following:

clear
syms x
solve(x^2 - 2*x - 4 == 0, x);