જો $u = \log_e(x^2 + y^2) + \tan^{-1}\left(\frac{y}{x}\right)$ હોય,તો $\frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = $

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

જો $u=\sin ^{-1}\left(\frac{x^4+y^4}{x+y}\right)$ હોય,તો $x \frac{\partial u}{\partial x}+y \frac{\partial u}{\partial y}$ ની કિંમત શોધો.

જો $u=f(r)$,જ્યાં $r^2=x^2+y^2$ હોય,તો $\left(\frac{\partial^2 u}{\partial x^2}+\frac{\partial^2 u}{\partial y^2}\right)$ ની કિંમત શું થાય?

જો $u = (x^2 + y^2 + z^2)^{3/2}$ હોય,તો $\left( \frac{\partial u}{\partial x} \right)^2 + \left( \frac{\partial u}{\partial y} \right)^2 + \left( \frac{\partial u}{\partial z} \right)^2 = $

જો $z = \sin^{-1}\left( \frac{x+y}{\sqrt{x} + \sqrt{y}} \right)$ હોય,તો $x\frac{\partial z}{\partial x} + y\frac{\partial z}{\partial y}$ ની કિંમત શોધો.