Red
This is a circle with center (h, k) at (0,0) and radius (r) = 6
Formula: (x - h)² + (y - k)² = r²
Answer: x² + y² = 36
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Blue
This is a circle with center (h, k) at (2,2) and radius (r) = 1
Formula: (x - h)² + (y - k)² = r²
Answer: (x - 2)² + (y - 2)² = 1
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Green:
This is a circle with center (h, k) at (-2,-2) and radius (r) = 1
Formula: (x - h)² + (y - k)² = r²
Answer: (x + 2)² + (y + 2)² = 1
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Purple:
This is an ellipse with center (h, k) at (0,-2) and radius on the x-axis (a) = 3 and radius on the x-axis (b) = 1
Formula:

Answer:

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Black:
This is a parabola with vertex (h, k) at (0,-6) and vertical stretch (a) = -1
Formula: y = a(x - h)² + k
Answer: y = -x² - 6