How to write an equation of a parabola

Me. i can't figure out this question. give an explanation too. .

Marquise has 200 meters of fencing to build a rectangular garden. the garden's area (in square meters) as a function of the garden's width w w (in meters) is modeled by: a ( w ) = − w 2 + 1 0 0 w a(w)=−w 2 +100w what side width will produce the maximum garden area? meters

Polynomials plz quick 1: subtract and simplify (–y^2 – 4y – 8) – (–4y^2 – 6y + 3)