Solution
= Solution
The <derivative> of the <parabola> is $dy/dx=2+2x$, giving <tangent line> slope $4$ at $(1,3)$. A <normal line to a plane curve> has the negative reciprocal slope, since its direction is <orthogonal> to a <tangent vector>. Hence
$$
\boxed{y-3=-\frac14(x-1),\qquad x+4y=13.}
$$
The point $(1,3)$ satisfies the equation, and the product of the two slopes is $-1$.