What is the magic number "i"

The roots of the function f(x) = x2 – 2x – 3 are shown. what is the missing number?

How is the equation of this circle written in standard form? x2 + y2 - 6x + 14y = 142 a) (x - 3)2 + (y + 7)2 = 200 b) (x+ 3)2 + (y - 7)2 = 200 (x - 6)2 + (y + 14)2 = 142 d) (x+6)2 + (y- 14)2 = 142

What ia the sum if the first 7 terms of the geometric series