Question 780806
The first graph is a parabola.  What is its x value when y = 21?  That's where it intersects the line y=21.<P>
21 = x^2 +5<P>
16 = x^2 so x = + or - 4.<P>
The points of intersection are (-4, 21) and (4, 21)<P>
The distance between the two points is 8 units.