f*B
is a matrix. So what is 1/(f*B)
? That is not defined in MATLAB. Do you mean inv(f*B)
?
In any event, the expression is clear if M = N = 1, so that f*B
is a scalar. In that case, because B >= 0
, 1/f*B
is convex, and therefore the objective is not concave, and the problem is not convex.