How do I do question 8?

The equation x2 – 1x – 90 = 0 has solutions {a, b}. what is a + b?

The equation of a circle is (x - 3)2 + (y - 7)2 = 25. determine the length of the radius. 4 25 12.5 5 write the standard equation of the circle with center (2, 3) and a diameter of 12. (x - 2)2 + (y - 3)2 = 36 (x + 2)2 + (y + 3)2 = 12 (x - 2)2 + (y - 3)2 = 6 (x - 3)2 + (y - 2)2 = 36 the equation of a circle is (x + 3)2 + (y + 7)2 = 25. where is (3, 4) located in relation to the circle? on the circle in the interior of the circle in the exterior of the circle at the center of the circle

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