What is the sum of
7x/x2-4 and 2/x+2

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

What function has a range {yly< 5}? question on picture above^

Find the value of x. also give me an explanation so i can complete it to other questions as well, : )