A garden plan puts the origin at the gate, with x and y measured in metres…

A garden plan puts the origin at the gate, with $x$ and $y$ measured in metres. A round pond has its centre at $(4, 1)$ and radius $6$ metres. Write the equation of the pond edge in the form $x^2 + y^2 + Dx + Ey + F = 0$. Then decide whether a bench at $(8, 5)$ is inside the pond, by finding the number $x^2 + y^2 + Dx + Ey + F$ at the bench. A negative number means inside.