Question: find the arc length

The graph shows the rate at which paint is used to paint a wall.enter values to complete each statement below based on the graph.when 1 gallon of paint has been used, ( # ) square feet of the wall will be painted.the unit rate is ( # )square feet per gallon.

Kylie explained that (-4x+9)^2 will result in a difference of squares because (-4x+9)^2 (-4x+9)^2 =(-4x)^2+(9)^2=16x^2+81

Can someone pls ! pls answer all. no explanation needed..