If the endpoints of the diameter of a circle are (8, −6) and (4, −2), what is the standard form equation of the circle? A) (x + 6)2 + (y − 4)2 = 22B) (x − 6)2 + (y + 4)2 = 22C) (x + 6)2 + (y − 4)2 = 8 D) (x − 6)2 + (y + 4)2 = 8
Question
Answer:
We do the midpoint formula to find the center of the circle to get the left side of the equation.Midpoint = [(X₁ + X₂) / 2 , (Y₁ + Y₂) / 2]
Now plug in:
[(8 + 4) / 2 , (- 6 - 2) / 2]
(12 / 2 , - 8 / 2)
(6, - 4)
The center of the circle is (6, -4)
Now we plug it into the equation of a circle:
(x - h)² + (y - k)² = r² where (h, k) is the center of the circle and r is the radius.
(x - 6)² + (y + 4)² = r² is the left side of the equation. This will eliminate options A and C
Now we do the distance formula using the center and an endpoint to get the radius. The formula for distance is:
√((X₂ - X₁)² + (Y₂ - Y₁)²)
We plug in using either of the endpoints.
√((4 - 6)² + (- 2 - (- 4))²)
√((-2)² + 2²)
√(4 + 4)
√8
√8 is your radius
(√8)² = 8
Your correct answer is (x - 6)² + (y + 4)² = 8, Option D
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