Chapter 13: Problem 47
Find the first partial derivatives of the following functions. $$f(w, x, y, z)=w^{2} x y^{2}+x y^{3} z^{2}$$
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Chapter 13: Problem 47
Find the first partial derivatives of the following functions. $$f(w, x, y, z)=w^{2} x y^{2}+x y^{3} z^{2}$$
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Assume that \(x+y+z=1\) with \(x \geq 0\), \(y \geq 0,\) and \(z \geq 0\). a. Find the maximum and minimum values of \(\left(1+x^{2}\right)\left(1+y^{2}\right)\left(1+z^{2}\right)\) b. Find the maximum and minimum values of \((1+\sqrt{x})(1+\sqrt{y})(1+\sqrt{z})\)
Use the gradient rules of Exercise 81 to find the gradient of the following functions. $$f(x, y, z)=\sqrt{25-x^{2}-y^{2}-z^{2}}$$
Use the formal definition of a limit to prove that $$\lim _{(x, y) \rightarrow(a, b)} y=b .(\text {Hint}: \text { Take } \delta=\varepsilon$$
In the advanced subject of complex variables, a function typically has the form \(f(x, y)=u(x, y)+i v(x, y),\) where \(u\) and \(v\) are real-valued functions and \(i=\sqrt{-1}\) is the imaginary unit. A function \(f=u+i v\) is said to be analytic (analogous to differentiable) if it satisfies the Cauchy-Riemann equations: \(u_{x}=v_{y}\) and \(u_{y}=-v_{x}\) a. Show that \(f(x, y)=\left(x^{2}-y^{2}\right)+i(2 x y)\) is analytic. b. Show that \(f(x, y)=x\left(x^{2}-3 y^{2}\right)+i y\left(3 x^{2}-y^{2}\right)\) is analytic. c. Show that if \(f=u+i v\) is analytic, then \(u_{x x}+u_{y y}=0\) and \(v_{x x}+v_{y y}=0\)
Use the gradient rules of Exercise 81 to find the gradient of the following functions. $$f(x, y, z)=(x+y+z) e^{x y z}$$
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