Explanation:
A trapezoid is a quadrilateral where at least one pair of opposite sides are parallel. Here Mr. Parker is graphing a quadrilateral, so he wants the quadrilateral to be a trapezoid. He has already graphed vertices at:
[tex](1, 1) \\ \\ (3, 3) \\ \\ (5, 3)[/tex]
So these points have been plotted below. As you can see form the graph, points (3, 3) and (5, 3) has the same y-coordinates, so the line that passes through these two points has zero slope. The other point is (1, 1) so we can choose any point such that the slope of the the line that passes through (1, 1) and that point also has zero slope. Therefore, the 4th vertex is any point of this form:
[tex]\boxed{(x,1)}[/tex]
