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

Verified Answer :

naǫ

The equation of a circle:
\((x-h)^2+(y-k)^2=r^2\)
(h,k) - the coordinates of the center
r - the radius

\(x^2+y^2+14x+2y+14=0 \\ x^2+14x+49+y^2+2y+1+14-49-1=0 \\ (x+7)^2+(y+1)^2+14-49-1=0 \\ (x+7)^2+(y+1)^2-36=0 \\ (x+7)^2+(y+1)^2=36 \\ (x-(-7))^2+(y-(-1))^2=6^2 \\ \Downarrow \\ h=-7 \\ k=-1 \\ r=6\)

The center is (-7,-1), the length of the radius is 6 units.
The answer is D.

Answer:

option d is correct.

center = (-7, -1)

r = 6

Step-by-step explanation:

The general equation of the circle is given by;

\((x-h)^2+(y-k)^2 = r^2\)

where;

(h, k) is the center of the circle

r is the radius of the circle respectively.

As per the statement:

A circle is described by the equation \(x^2 + y^2 + 14x + 2y + 14 = 0\)

then;

\((x^2+14x)+(y^2 + 2y) + 14 = 0\)

Using the completing the square:

\((x^2+14x+7^2-7^2)+(y^2 + 2y+1^2-1^2) + 14 = 0\)

⇒\((x+7)^2 - 49 + (y+1)^2 - 1 + 14 = 0\)

⇒ \((x+7)^2+(y+1)^2 -36 = 0\)

Add 36 to both sides we have;

\((x+7)^2+(y+1)^2=36\)

On comparing with the general equation of circle:

we get;

h = -7 ,  k = -1 and \(r^2 = 36\)

⇒\(r = 6\)

Therefore, the coordinate of the center of the circle is (-7, -1) and length of the radius of the circle is 6