Missing two closing parenthesis it would appear. Is MATLAB suggestion not correct? You might do better breaking this up into multiple lines using the ... operator notation for easier readability.
>> dwdx=@(X)ks*(((FA0.*(1-X).*R.*T.*y)./(v.*(1+esp.*X)))-(((FA0.*(theta_B+X).*R.*T.*y)/(v.*(1+esp.*X))*((FA0.*(theta_C+X).*R.*T.*y)/(v.*(1+esp.*X)))/(Ke)))/(((1+(KA.*(FA0.*(1-X).*R.*T.*y)./(v.*(1+esp.*X)))+(KB.*(FA0.*(theta_B+X).*R.*T.*y)/(v.*(1+esp.*X)))+(KC.*(FA0.*(theta_C+X).*R.*T.*y)/(v.*(1+esp.*X)))).^2);
dwdx=@(X)ks*(((FA0.*(1-X).*R.*T.*y)./(v.*(1+esp.*X)))-(((FA0.*(theta_B+X).*R.*T.*y)/(v.*(1+esp.*X))*((FA0.*(theta_C+X).*R.*T.*y)/(v.*(1+esp.*X)))/(Ke)))/(((1+(KA.*(FA0.*(1-X).*R.*T.*y)./(v.*(1+esp.*X)))+(KB.*(FA0.*(theta_B+X).*R.*T.*y)/(v.*(1+esp.*X)))+(KC.*(FA0.*(theta_C+X).*R.*T.*y)/(v.*(1+esp.*X)))).^2);
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Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.
Did you mean:
>> dwdx=@(X)ks*(((FA0.*(1-X).*R.*T.*y)./(v.*(1+eps.*X)))-(((FA0.*(theta_B+X).*R.*T.*y)/(v.*(1+eps.*X))*((FA0.*(theta_C+X).*R.*T.*y)/(v.*(1+eps.*X)))/(Ke)))/(((1+(KA.*(FA0.*(1-X).*R.*T.*y)./(v.*(1+eps.*X)))+(db.*(FA0.*(theta_B+X).*R.*T.*y)/(v.*(1+eps.*X)))+(KC.*(FA0.*(theta_C+X).*R.*T.*y)/(v.*(1+eps.*X)))).^2)));
