MATLAB: How to solve this equation

equationplot

I have this equation and it seems hard to calculate manually so I decided to write a code… but I cannot 🙁

a+b*x=x/(b*ln((x-e)/x));

Only x is the variable, a,b and e is known.

Thank!

Best Answer

syms x
eqn = a+b*x==x/(b*log((x-e)/x));
vpasolve(eqn, x)

eqn = @(x) (a+b*x) - (x/(b*log((x-e)/x)));
fzero(eqn, InitialGuess)

Related Solutions

MATLAB: Solve and plot symbolic equation

   plot(t, subs(X,'t',t) )

Which is to say that if you use a symbolic variable in an expression and later assign a numeric value to the symbol, then the expressions that used the symbolic variable are not automatically updated to use the numeric value.

The situation is exactly the same as if you had used

A = 1;
B = A + 10;
A = 15;

then afterwards, B is not updated to 25, because at the time the B=A+10 is executed, the value of A (1) is extracted and used.

syms A
B = A + 10;
A = 15;

then afterwards B is not updated to 25, because at the time the B=A+10 is executed, the value of A (sym('A')) is extracted and used.

The line

syms A

is the same as

A = sym('A');

This does not make A identical to the symbol named 'A': it establishes a link to the symbol named 'A', and

B = A + 10;

would copy that link to the symbol named 'A', not a link to the variable named 'A'.

A = 15;

would break the link between the variable named 'A' and the symbol named 'A', but B does not refer to the variable so B does not get updated to evaluate to 25: it still has the link to the symbol named 'A'.

Symbols themselves live in a different workspace (effectively).

MATLAB: How to use “fsolve” to solve nonlinear simultaneous equations

Thanks, everyone.

I have solved the problem by myself.

syms x1 x2
equ1=x1^2 - 1;
equ2=x2*x1 - 3;
equs=[equ1;equ2];
myfun = matlabFunction(equs);
fun= @(x) myfun(x(1),x(2))
solve= fsolve(fun, [0, 0])

Best Answer

Related Solutions

MATLAB: Solve and plot symbolic equation

MATLAB: How to use “fsolve” to solve nonlinear simultaneous equations

Related Question