Hi vaya putra
This error comes out because you are basically adding two "functions". What you want to do is probably adding two functions "output"
So, you should make another function which takes inputs and feed them to each function and add the output
this is an example.
q1 = @(a,b) a+b;
q2 = @(a,b) a*b;
q3 = @(a,b) q1(a,b) + q2(a,b);
for your code, this might help
q_conn = @(p,T, bhp) q1(p,T, bhp)+q2(p,T, bhp)
