Which of the following relations is a function?
{ (1, 2), (1, 3), (1, 4), (1, 5) }
{ (1, 3), (2, 3), (4, 3), (9, 3) }
{ (5, 4), (-6, 5), (4, 5), (4, 0) }
{ (6, -1), (1, 4), (2, 3), (6, 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

Carley bought a jacket that was discounted 10% off the original price. the expression below represents the discounted price in dollars, based on x, the original price of the jacket.

Agallon of apple juice cost $7 a pack of eight 4.23oz box of apple juice $2.39 which is a better deal