The vertex of a parabola is the point at the intersection of the parabola and its line of symmetry. The vertex will be the minimum (lowest point) of the graph OR the maximum (highest point), depending on whether it's a negative or positive parabola. In this case, that point is (-1,8).
If two lines have the same slope and different intercepts, then they will never cross each other; they are parallel lines. Therefore, they have no solutions since a solution is where the lines cross.
