11th grade math circles question

Write the center and the radius of this circle: x^2 + y^2 + 8x - 2y -15 = 0

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x^2 + y^2 + 8x - 2y -15 = 0

x^2 + y^2 + 8x - 2y =15

(x^2 + 8x) + (y^2 - 2y) =15

complete the sqaure for x terms with (b/2)^2 = (8/2)^2 = 16

complete the square for y terms with (b/20^2 = (2/2)^2 = 1^2 = 1

(x^2 + 8x + 16) + (y^2 - 2y + 1) = 15 + 16 + 1

(x + 4)^2 + (y - 1)^2 = 32

center (- 4,1) with radius of sqrt(32) = 4sqrt(2)