Which of the following functions f(x,y)f(x,y)f(x,y) satisfies Laplace's equation ∇2f=0\nabla^2 f = 0∇2f=0?
f(x,y)=x2+y2f(x,y) = x^2 + y^2f(x,y)=x2+y2
f(x,y)=exsinyf(x,y) = e^x \sin yf(x,y)=exsiny
f(x,y)=x3−3xy2f(x,y) = x^3 - 3xy^2f(x,y)=x3−3xy2
f(x,y)=x2−y2f(x,y) = x^2 - y^2f(x,y)=x2−y2