Select the correct answer.

Which equation represents a circle with center [tex]Z(-3,5)[/tex] and a radius of 4 units?

A. [tex](x-3)^2+(y+5)^2=4[/tex]
B. [tex](x-3)^2+(y+5)^2=16[/tex]
C. [tex](x+3)^2+(y-5)^2=4[/tex]
D. [tex](x+3)^2+(y-5)^2=16[/tex]



Answer :

To determine which equation represents a circle with a center at [tex]\( Z(-3, 5) \)[/tex] and a radius of 4 units, we need to use the standard form of the equation of a circle:

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

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

### Step-by-Step Solution:

1. Identify the center [tex]\((h, k)\)[/tex] and the radius [tex]\(r\)[/tex]:

- The center [tex]\((h, k)\)[/tex] is given as [tex]\((-3, 5)\)[/tex].
- The radius [tex]\(r\)[/tex] is given as 4 units.

2. Substitute the values into the standard equation:

- [tex]\(h = -3\)[/tex]
- [tex]\(k = 5\)[/tex]
- [tex]\(r = 4\)[/tex]

3. Write the equation with the given center and radius:

- Substitute [tex]\(h = -3\)[/tex] and [tex]\(k = 5\)[/tex] into the equation:

[tex]\[ (x - (-3))^2 + (y - 5)^2 = 4^2 \][/tex]

- Simplify the terms:

[tex]\[ (x + 3)^2 + (y - 5)^2 = 16 \][/tex]

4. Match the derived equation with the given options:

Let's look at each of the options provided:

A. [tex]\((x-3)^2 + (y+5)^2 = 4\)[/tex]

- Here, the center would be [tex]\((3, -5)\)[/tex] and the radius squared would be 4, which does not match our parameters.

B. [tex]\((x-3)^2 + (y+5)^2 = 16\)[/tex]

- Here, the center would be [tex]\((3, -5)\)[/tex] and the radius squared is 16. Though the radius squared is correct, the center does not match our parameters.

C. [tex]\((x+3)^2 + (y-5)^2 = 4\)[/tex]

- Here, the center would be [tex]\((-3, 5)\)[/tex] but the radius squared is 4, which does not match our parameters.

D. [tex]\((x+3)^2 + (y-5)^2 = 16\)[/tex]

- Here, the center is [tex]\((-3, 5)\)[/tex] and the radius squared is 16. This perfectly matches our derived equation.

The correct answer is:

[tex]\[ \boxed{(x+3)^2 + (y-5)^2 = 16} \][/tex]

Thus, the equation representing a circle with center [tex]\( Z(-3, 5) \)[/tex] and a radius of 4 units is:

D. [tex]\((x+3)^2+(y-5)^2=16\)[/tex]