a. The top of the graph illustrated has a value of y = 4, so you need to solve the equation (x-2)2 - 1 = 4 (this is a quadratic equation and will produce two values for x).
b. Assuming this means the intersection of the curve with the horizontal line at y = 5, there will be two points of intersection.
c. Since 'a' gives the y-coordinate of the vertex (lowest point), then when a>0 the curve will not intyersect the x-axis.