Square one factor from column a and add it to one factor from column b to develop your own identity.
column a column b
(x-y) (x^2+2xy+y^2)
(x+y) (x2 − 2xy + y2)
(y+x) (ax + b)
(y-x) (cy + d)

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters