I know the definition of the Jacobian and hessian of $x$. However, I am confused how to find the jacobian and hessian of $z=Ax+b$. $A$ is an $m\times n$ matrix and b is a $m\times 1$ vector.
Hessian matrix of a vector-valued function is a third order tensor of the form: $H(z)=[H(f1) H(f2) \dots H(fm)]$