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The equation of a circle which has a center at (-5,2) can be written as Ax^2 + 2y^2 + Bx + Cy = 40. Find the radius of the circle.

 Feb 11, 2019
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\((x+5)^2+(y-2)^2 = r^2\\ x^2 + 10x + 25 + y^2 - 2y+4 = r^2\\ x^2 + 10x + y^2 -2y = r^2 -29\\ 2x^2 + 20x +2y^2 - 4y = 2r^2 - 58 = 40\\ 2r^2 = 98\\ r^2 = 49\\ r = 7\)

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 Feb 11, 2019

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