2) Tìm các giá trị của x để biểu thức M = (x + 5).(x + 9)
a) có giá trị dương. b) có giá trị âm

Ineed to know the answer to this algebra question.

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

Plz hurry evaluate the expression a+b where a=8 and b=19