Which equation represents the circle described?

- The radius is 2 units.
- The center is the same as the center of a circle whose equation is [tex]x^2 + y^2 - 8x - 6y + 24 = 0[/tex].

A. [tex]\((x+4)^2 + (y+3)^2 = 2\)[/tex]
B. [tex]\((x-4)^2 + (y-3)^2 = 2\)[/tex]
C. [tex]\((x-4)^2 + (y-3)^2 = 2^2\)[/tex]
D. [tex]\((x+4)^2 + (y+3)^2 = 2^2\)[/tex]



Answer :

To determine the equation of the circle with a radius of 2 units and the same center as a circle whose equation is given by [tex]\( x^2 + y^2 - 8x - 6y + 24 = 0 \)[/tex], we follow these steps:

1. Start with the given equation of the circle: [tex]\( x^2 + y^2 - 8x - 6y + 24 = 0 \)[/tex].

2. We need to find the center of this circle. To do this, we will complete the square for both the [tex]\( x \)[/tex] and [tex]\( y \)[/tex] terms.

3. Rewrite the equation by grouping the [tex]\( x \)[/tex] and [tex]\( y \)[/tex] terms:
[tex]\[ x^2 - 8x + y^2 - 6y + 24 = 0 \][/tex]

4. Complete the square for the [tex]\( x \)[/tex] terms:
[tex]\[ x^2 - 8x \rightarrow (x - 4)^2 - 16 \][/tex]

5. Complete the square for the [tex]\( y \)[/tex] terms:
[tex]\[ y^2 - 6y \rightarrow (y - 3)^2 - 9 \][/tex]

6. Substitute the completed squares back into the equation:
[tex]\[ (x - 4)^2 - 16 + (y - 3)^2 - 9 + 24 = 0 \][/tex]

7. Simplify the equation:
[tex]\[ (x - 4)^2 + (y - 3)^2 - 25 + 24 = 0 \][/tex]
[tex]\[ (x - 4)^2 + (y - 3)^2 - 1 = 0 \][/tex]
[tex]\[ (x - 4)^2 + (y - 3)^2 = 1 \][/tex]

8. The center of the original circle is [tex]\((4, 3)\)[/tex].

9. Now, given that we need to find an equation of a new circle with a radius of 2 units and the same center [tex]\((4, 3)\)[/tex], we start with the standard form of a circle equation:
[tex]\[ (x - h)^2 + (y - k)^2 = r^2 \][/tex]

where [tex]\((h, k)\)[/tex] is the center and [tex]\(r\)[/tex] is the radius.

10. Substitute [tex]\(h = 4\)[/tex], [tex]\(k = 3\)[/tex], and [tex]\(r = 2\)[/tex]:
[tex]\[ (x - 4)^2 + (y - 3)^2 = 2^2 \][/tex]

11. Simplify:
[tex]\[ (x - 4)^2 + (y - 3)^2 = 4 \][/tex]

Therefore, the equation that represents the new circle is:
[tex]\[ (x - 4)^2 + (y - 3)^2 = 4 \][/tex]

So the correct choice among the given options is:
[tex]\[ (x - 4)^2 + (y - 3)^2 = 2^2 \][/tex]