Solution
= Solution
The only contributions to the <Laplacian> come from the pure quadratic terms. Hence
$$
\boxed{\nabla^2\phi=1+1-2=0.}
$$
The scalar potential is therefore a <harmonic function>. Since $\mathbf F=\nabla\phi$,
$$
\boxed{\nabla\cdot\mathbf F=\nabla\cdot\nabla\phi=0.}
$$
Thus this field is both <irrotational> and divergence-free. By the <divergence theorem>, its net flux through every sufficiently regular closed surface is zero.