Question
Show that the function $u(x, y, t)=t^{-1} e^{-\left(x^{2}+y^{2}\right) / 4 t}$ satisfies the two-dimensional heat equation $$\frac{\partial u}{\partial t}=\frac{\partial^{2} u}{\partial x^{2}}+\frac{\partial^{2} u}{\partial y^{2}}$$
Step 1
Using the chain rule, we have \begin{align*} \frac{\partial u}{\partial t} &= \frac{\partial}{\partial t} \left(t^{-1} e^{-\left(x^{2}+y^{2}\right) / 4 t}\right) \\ &= -t^{-2} e^{-\left(x^{2}+y^{2}\right) / 4 t} + \frac{x^{2}+y^{2}}{4t^{3}} Show more…
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