Answer:
(x + 3)² + (y + 1)² = 100
Explanation:
Equation of a circle is:
(x − h)² + (y − k)² = r²
where (h, k) is the center of the circle and r is the radius.
The center is on the line x − 4y = 1, so:
h − 4k = 1
h = 1 + 4k
(x − 1 − 4k)² + (y − k)² = r²
Two points on the line are (3, 7) and (5, 5), so:
(3 − 1 − 4k)² + (7 − k)² = r²
(5 − 1 − 4k)² + (5 − k)² = r²
Set the equations equal:
(3 − 1 − 4k)² + (7 − k)² = (5 − 1 − 4k)² + (5 − k)²
(2 − 4k)² + (7 − k)² = (4 − 4k)² + (5 − k)²
4 − 16k + 16k² + 49 − 14k + k² = 16 − 32k + 16k² + 25 − 10k + k²
4 − 16k + 49 − 14k = 16 − 32k + 25 − 10k
53 − 30k = 41 − 42k
12k = -12
k = -1
h = 1 + 4k
h = -3
(3 − 1 − 4k)² + (7 − k)² = r²
(3 − 1 + 4)² + (7 + 1)² = r²
6² + 8² = r²
r = 10
Therefore, the equation of the circle is:
(x + 3)² + (y + 1)² = 10²