Answer
$$sech^2 (x+2y+3z) \\ 2sech^2 (x+2y+3z) \\ 3 \space sech^2 (x+2y+3z)$$
Work Step by Step
$f_x=sech^2 (x+2y+3z) \times \dfrac{\partial }{\partial x} (x+2y-3z)=sech^2 (x+2y+3z)$
$f_y=sech^2 (x+2y+3z) \times \dfrac{\partial}{\partial y} (x+2y-3z)=2sech^2 (x+2y+3z)$
$f_z= sech^2 (x+2y+3z) \times \dfrac{\partial }{\partial z} (x+2y-3z) =3 \space sech^2 (x+2y+3z)$
