Liam - according to the documentation for fzero, the input function handle is to a function that a accepts a scalar x and returns a scalar fun(x). Note that your function accepts four inputs, and so the error message, Not enough input arguments, makes sense since there fsolve will only try to provide one.
If x is your only variable into SCC, and the remaining three parameters, A, B, and C, are constant, then I would replace your line of code
q=fzero('SCC',1);
with an anonymous function that makes use of SCC as
q=fzero(@(x)SCC(x,A,B,C),1);
In the above, we are now supplying a function to fzero that will accept a single input argument only, and use the A, B, and C that have been defined previously. See anonymous functions for more details.
Try the above and see what happens!
