Question: Complete the equation of the circle $x^2 + y^2 + 2x - 6y + 6 = 0$ in standard form. Identify the center and radius, then select the correct graph of the circle.
$(x + 1)^2 + (y - 3)^2 = 4$
The center is $C(-1, 3)$ and the radius is $r = 4$.
Graph shapes:
A: circle centered near $(1, -3)$, radius about $2$.
B: circle centered near $(1, 3)$, radius about $2$.
C: circle centered below the x-axis, partially visible.
D: circle centered near $(-1, 3)$, radius about $2$.
position_hint: centerUser:
1. **State the problem:**
We are given the circle equation $$x^2 + y^2 + 2x - 6y + 6 = 0$$ and need to write it in standard form, identify the center and radius, and select the correct graph.
2. **Recall the standard form of a circle:**
$$ (x - h)^2 + (y - k)^2 = r^2 $$
where $(h, k)$ is the center and $r$ is the radius.
3. **Complete the square for $x$ and $y$ terms:**
Group $x$ and $y$ terms:
$$ x^2 + 2x + y^2 - 6y = -6 $$
Complete the square for $x$:
$$ x^2 + 2x = (x^2 + 2x + 1) - 1 = (x + 1)^2 - 1 $$
Complete the square for $y$:
$$ y^2 - 6y = (y^2 - 6y + 9) - 9 = (y - 3)^2 - 9 $$
4. **Rewrite the equation with completed squares:**
$$ (x + 1)^2 - 1 + (y - 3)^2 - 9 = -6 $$
Simplify the constants:
$$ (x + 1)^2 + (y - 3)^2 - 10 = -6 $$
Add $10$ to both sides:
$$ (x + 1)^2 + (y - 3)^2 = 4 $$
5. **Identify the center and radius:**
Center: $C(-1, 3)$
Radius: $r = \sqrt{4} = 2$
6. **Select the correct graph:**
The circle is centered at $(-1, 3)$ with radius $2$, so the correct graph is **D**.
**Final answer:**
Standard form: $$ (x + 1)^2 + (y - 3)^2 = 4 $$
Center: $(-1, 3)$
Radius: $2$
Graph: D