调和函数的定义为∂^2(u)/∂x^2+∂^2(u)/∂y^2=0.对u(x,y)=x^2+xy-y^2,∂u/∂x=2x+y,所以∂^2(u)/∂x^2=2；∂u/∂y=x-2y,所以∂^2(u)/∂y^2=-2.所以&#...