1.

Assume that Φ is harmonic in domain D and for x0 ∈ D, B(x0, r) ⊆ D, then the average value of Φ over the boundary of B(x0, r) equals

A. \({\rm{\Phi }}\left( {{x_0}} \right)\)
B. \(r{\rm{\Phi }}\left( {{x_0}} \right)\)
C. \(\frac{1}{{\pi r}}{\rm{\Phi }}\left( x \right)\)
D. \(\frac{4}{3}\pi {r^3}{\rm{\Phi }}\left( x \right)\)
Answer» B. \(r{\rm{\Phi }}\left( {{x_0}} \right)\)


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