Gilbert Strang, Calculus, 3rd edition (Wellesley-Cambridge Press; MIT OpenCourseWare RES.18-001) §13.5 The Chain Rule, #47 · Multivariable Calculus · Partial derivatives

(horrible) Suppose

(horrible) Suppose $f_{xx} + f_{y y} = 0$ . If $x = u + v$ and $y = u - v$ and $f (x, y) = g (u, v)$ , find $g_{u}$ and $g_{v}$ . Show that $g_{uu} + g_{v v} = 0$ .

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Gilbert Strang, Calculus, 3rd edition (Wellesley-Cambridge Press; MIT OpenCourseWare RES.18-001) · §13.5 The Chain Rule, #47

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