How to get the special trinomial given the binomial

Answer these questions showing your work plz

Acircular city park has a sidewalk directly through the middle that is 111 - feet long. if each bag of fertilizer covers 50 square feet, then determine how many bags of fertilizers the parks and recreation department needs to use to cover the circular park. ignore all the sidewalks around and through the park.

The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.