20 points
When you find a point on a graph that you think is the intersection, the best way to double check your answer is to:
substitute in the x value to see if both of the y values of both of the equations match the one you approximated from the graph.
substitute in the x value to see if one of the y values of one of the equations matches the one you approximated from the graph.
substitute in the y value to see if one of the x values of one of the equations matches the one you approximated from the graph.
substitute in the x value to see if both of the x values of both of the equations match the one you approximated from the graph.