Find all real-valued functions on the reals such that (f(x)+f(y))(f(u)+f(v))=f(xu−yv)+f(xv+yu)(f(x)+f(y))(f(u)+f(v))=f(xu-yv)+f(xv+yu)(f(x)+f(y))(f(u)+f(v))=f(xu−yv)+f(xv+yu) for all x,y,u,vx,y,u,vx,y,u,v.