摘要
本文在ｕ为二次连续可微的前提下，证明如果ｕ满足平均值定理，则ｕ为调和函数。证明仅用到ｇｒｅｅｎ公式。
We now reprove that if u is a twice continuously differentiable function satisfied the reverse avargevalued theorem then it is harmonic. The proof utilizes only the Green formula.
关键词
调和函数
格林公式
逆平均值定理
harmonic function
avargevalued theorem
Green formula
