Question

Найти производные функций двух переменных dz/dx, dz/dy z=u^2 *Sqrt[u-v] u=x+2y v=xy

Answer 1

$z=u^2\cdot \sqrt{u-v}\; \; ,\; \; u=x+2y\; ,\; v=xy\\\\z=z(\, u(x,y)\, ;\, v(x,y)\, )\\\\\\\frac{\partial z}{\partial x}=\frac{\partial z}{\partial u} \cdot \frac{\partial u}{\partial x}+\frac{\partial z}{\partial v}\cdot \frac{\partial v}{\partial x}=\\\\=\Big (2u\cdot \sqrt{u-v}+u^2\cdot \frac{1}{2\sqrt{u-v}}\Big )\cdot 1+u^2\cdot \frac{-1}{2\sqrt{u-v}}\cdot y=\\\\=2u\cdot \sqrt{u-v}+\frac{u^2}{2\sqrt{u-v}}\cdot (1-y)$

$\frac{\partial z}{\partial y}=\frac{\partial z}{\partial u} \cdot \frac{\partial u}{\partial y}+\frac{\partial z}{\partial v}\cdot \frac{\partial v}{\partial y}=\\\\=\Big (2u\cdot \sqrt{u-v}+u^2\cdot \frac{1}{2\sqrt{u-v}}\Big )\cdot 2+u^2\cdot \frac{-1}{2\sqrt{u-v}}\cdot x=\\\\=4u\cdot \sqrt{u-v}+\frac{u^2}{2\sqrt{u-v}}\cdot (2-x)$