Get comprehensive solutions to your questions with the help of IDNLearn.com's experts. Discover trustworthy solutions to your questions quickly and accurately with help from our dedicated community of experts.

Mrs. Culland is finding the center of a circle whose equation is [tex]x^2 + y^2 + 6x + 4y - 3 = 0[/tex] by completing the square. Her work is shown.

[tex]\[
\begin{array}{l}
x^2 + y^2 + 6x + 4y - 3 = 0 \\
x^2 + 6x + y^2 + 4y - 3 = 0 \\
\left(x^2 + 6x\right) + \left(y^2 + 4y\right) = 3 \\
\left(x^2 + 6x + \underline{9}\right) + \left(y^2 + 4y + \underline{4}\right) = 3 + \underline{9} + \underline{4}
\end{array}
\][/tex]

Which completes the work correctly?

A. [tex]\((x-3)^2 + (y-2)^2 = 4^2\)[/tex], so the center is [tex]\((3, 2)\)[/tex].

B. [tex]\((x+3)^2 + (y+2)^2 = 4^2\)[/tex], so the center is [tex]\((3, 2)\)[/tex].

C. [tex]\((x-3)^2 + (y-2)^2 = 4^2\)[/tex], so the center is [tex]\((-3, -2)\)[/tex].

D. [tex]\((x+3)^2 + (y+2)^2 = 4^2\)[/tex], so the center is [tex]\((-3, -2)\)[/tex].


Sagot :

Let's work through completing the square for the given equation of the circle step-by-step to identify the center and the radius correctly.

Given equation:
[tex]\[ x^2 + y^2 + 6x + 4y - 3 = 0 \][/tex]

1. Rearrange terms to isolate [tex]\(x\)[/tex] and [tex]\(y\)[/tex]:
[tex]\[ x^2 + 6x + y^2 + 4y - 3 = 0 \][/tex]

2. Group the [tex]\(x\)[/tex] terms and [tex]\(y\)[/tex] terms together:
[tex]\[ (x^2 + 6x) + (y^2 + 4y) = 3 \][/tex]

3. Complete the square for the [tex]\(x\)[/tex] terms. To do this, take half of the coefficient of [tex]\(x\)[/tex] (which is 6), square it, and add it inside the parenthesis:
[tex]\[ x^2 + 6x \][/tex]
Take [tex]\( \left(\frac{6}{2}\right)^2 = 9 \)[/tex].
So, we rewrite [tex]\(x^2 + 6x\)[/tex] as:
[tex]\[ (x + 3)^2 - 9 \][/tex]

4. Complete the square for the [tex]\(y\)[/tex] terms. Similarly, take half of the coefficient of [tex]\(y\)[/tex] (which is 4), square it, and add it inside the parenthesis:
[tex]\[ y^2 + 4y \][/tex]
Take [tex]\( \left(\frac{4}{2}\right)^2 = 4 \)[/tex].
So, we rewrite [tex]\(y^2 + 4y\)[/tex] as:
[tex]\[ (y + 2)^2 - 4 \][/tex]

5. Substitute these completed square forms back into the original equation:
[tex]\[ (x + 3)^2 - 9 + (y + 2)^2 - 4 = 3 \][/tex]

6. Simplify the equation:
[tex]\[ (x + 3)^2 + (y + 2)^2 - 9 - 4 = 3 \][/tex]
[tex]\[ (x + 3)^2 + (y + 2)^2 - 13 = 3 \][/tex]
[tex]\[ (x + 3)^2 + (y + 2)^2 = 16 \][/tex]

7. Write the equation in standard form:
[tex]\[ (x + 3)^2 + (y + 2)^2 = 4^2 \][/tex]

From this equation, the center of the circle [tex]\((h, k)\)[/tex] is [tex]\((-3, -2)\)[/tex] and the radius [tex]\( r \)[/tex] is 4.

So, the correct completion of the work is:
[tex]\[ (x + 3)^2 + (y + 2)^2 = 4^2 \][/tex]

Therefore, the center is [tex]\((-3, -2)\)[/tex] and the correct completion sentence is:
[tex]\[ \boxed{(x+3)^2+(y+2)^2=4^2,\ \text{so the center is}\ (-3, -2).} \][/tex]
We value your participation in this forum. Keep exploring, asking questions, and sharing your insights with the community. Together, we can find the best solutions. IDNLearn.com is your go-to source for accurate answers. Thanks for stopping by, and come back for more helpful information.