Max points

so previously i answered,

(a) start by writing the equation of the circle. (recall that the general form of a circle with the center at the origin is x2 + y2 = r2. (10 points) x^2 + y^2 = 30^2

and

(b) now solve this equation for y. remember the roller coaster is above ground, so you are only interested in the positive root. (10 points) y = √(900 - x^2)

now i have to solve this in the image attached,

any ideas?