2.3.21 Gradient and directional derivative

Problem: Find the derivative of function \( \varphi \) at point \( A \) in the direction of vector \( \overrightarrow{A B} \) : \[ \varphi=\frac{y^{2}}{x}+\frac{y^{2}}{z}+\frac{z^{2}}{x^{2}}, \quad A(1 ; 0 ; 1), \quad B(2 ; 2 ; 3) . \]