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

Answer 1

$x^{2}+y^{2}+14x+2y+14=0 \\ \\ x^{2}+14x+49 +y^{2}+2y+1-36=0 \\ \\ (x+7)^{2}+(y+1)^{2}=36 \\ \\ S=(-7,-1) \\ \\ r=6$

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$(x-a)^{2}+(y-b)^{2}=r^{2} \\ \\ S=(a,b)$