func = @(x) coeff1*x.^exp1 + coeff2*x.exp2 + b;
x0 = 1; % starting point
roots = fzero(func,x0)
In the above code snippet, you can define your function, choose a starting point and fzero will give you the roots. It is generally a good idea to plot your function to get an idea of what it looks like. You can do that in the following manner:
x_interval = -10:10
fplot(func,x_interval)
