Need help. Can’t figure this problem out

Write the expression 7x^3-28xy^2 as the product of 3 factors

True or false: the graph of y=f(bx) is a horizontal compression of the graph y=f(x) if b< 1

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