In MATLAB, a vector is consider a single input. If you want to pass you input as vector then change your function like this
function x=man(in)
V = in(1);
VF = in(2);
y = in(3);
L = in(4);
D = in(5);
x=(V+VF)*y/(L+D);
end
and then call it like this
a = [1, 2, 3, 4, 5];
man(a)
But if you want to stick to the current definition, then the other option is to use cell array. For example, keep using your current definition of 'man' and run the following lines
a = {1, 2, 3, 4, 5};
man(a{:})
