यदि $u = \log_e(x^2 + y^2) + \tan^{-1}\left(\frac{y}{x}\right)$ है,तो $\frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = $

यदि $u = \frac{x + y}{x - y}$ है,तो $\frac{\partial u}{\partial x} + \frac{\partial u}{\partial y} = $

यदि $z = \frac{y}{x} \left[ \sin \left( \frac{x}{y} \right) + \cos \left( 1 + \frac{y}{x} \right) \right]$ है,तो $x \frac{\partial z}{\partial x} = $

यदि $u = x y^2 \tan^{-1}\left(\frac{y}{x}\right)$ है,तो $x \frac{\partial u}{\partial x} + y \frac{\partial u}{\partial y}$ का मान ज्ञात कीजिए।

$\begin{aligned} & f(x, y)=2(x-y)^2-x^4-y^4 \\ & \left|\left(f_{x x} f_{y y}-f_{x y}^2\right)\right|_{(0,0)} \end{aligned}$

यदि $u = \sin^{-1}\left(\frac{x}{y}\right) + \tan^{-1}\left(\frac{y}{x}\right)$ है, तो $x \frac{\partial u}{\partial x} + y \frac{\partial u}{\partial y}$ का मान क्या है?