Question

Find equation of the plane through the point (3,-1,1) parallel to the xy-plane

Answer 1

A plane parallel to the xy plane always have the equation
\[z=k\]
Where k is a constant we have to determine using the point they give you. As the plane must have the point (3,-1,1), plug in into the equation,
\[z=1\]
And this is the plane.