Which equation describes the circle that is centered at [tex]\((-5,7)\)[/tex] and has a radius of [tex]\(11\)[/tex]?

A. [tex]\((x-5)^2+(y+7)^2=121\)[/tex]
B. [tex]\((x+5)^2+(y-7)^2=11\)[/tex]
C. [tex]\((x+5)^2+(y-7)^2=121\)[/tex]
D. [tex]\((x-5)^2+(y+7)^2=11\)[/tex]



Answer :

To determine which equation describes the circle, we need to use the standard form of the equation of a circle.

The standard form equation of a circle centered at [tex]\((h, k)\)[/tex] with radius [tex]\(r\)[/tex] is:

[tex]\[ (x - h)^2 + (y - k)^2 = r^2 \][/tex]

Given:
- The center of the circle is [tex]\((-5, 7)\)[/tex], so [tex]\(h = -5\)[/tex] and [tex]\(k = 7\)[/tex].
- The radius is [tex]\(11\)[/tex], so [tex]\(r = 11\)[/tex].

Let's substitute these values into the standard form equation.

1. Plug the center coordinates [tex]\((-5, 7)\)[/tex] into the formula:
[tex]\[ (x - (-5))^2 + (y - 7)^2 = r^2 \][/tex]
Simplify the equation where needed:
[tex]\[ (x + 5)^2 + (y - 7)^2 = r^2 \][/tex]

2. Replace the radius [tex]\(r\)[/tex] with [tex]\(11\)[/tex]:
[tex]\[ (x + 5)^2 + (y - 7)^2 = 11^2 \][/tex]

3. Calculate the square of the radius:
[tex]\[ 11^2 = 121 \][/tex]

Now substituting back, we get:
[tex]\[ (x + 5)^2 + (y - 7)^2 = 121 \][/tex]

So, the correct equation that describes the circle centered at [tex]\((-5, 7)\)[/tex] with a radius of [tex]\(11\)[/tex] is:
[tex]\[ (x + 5)^2 + (y - 7)^2 = 121 \][/tex]

Therefore, the correct answer from the given options is:
[tex]\[ (x + 5)^2 + (y - 7)^2 = 121 \][/tex]