Visualizing epsilon & delta

The graph of y = x^2 is shown in the graph. An interval on the x-axis has been created for you. The point in the middle and the left end-point can both move to change the width of the box. The y-coordinate of the point is indicated by the dotted red line. How close to the x-value do the ends of the interval need to be in order for the height of the box to be less than 0.5?