Question

A circle is described by the equation x2 + y2 + 14x + 2y + 14 = 0. What are the coordinates for the center of the circle and the length of the radius?
A)(-7, -1), 36 units

B)(7, 1), 36 units

C)(7, 1), 6 units

D)(-7, -1), 6 units
help me plz

Answer 1

x^2 + y^2 + 14x + 2y + 14 = 0.
is compare with x^2 + y^2 + 2gx + 2fy + c= 0.
Center (-g,-f)
Radius r =sqrt(g^2+f^2-c)
2g =14
g=7
2f= 2
f =1
c=14
Center, C =(-g,-f) =(-7,-1)
Radius r= sqrt(7^2+1^2-14)
=sqrt(49+1-14)
=sqrt(36)
=6
Option D is correct
Source: http://www.mathskey.com/question2answer/