How do you find the center and the radius of the circle; the graph the circle of x2+y2+8x−8y−93=0?

1 Answer
Roella W.
Jan 20, 2016

The centre is (−4,4) and the radius is 5√5

Explanation:

The standard form of a circle is (x−h)2+(y−k)2=r2

To get this equation into the right form, start by grouping like terms.
x2+8x+y2−8y=93
(x+4)2−16+(y−4)2−16=93
(x+4)2+(y−4)2=93+32=125

(x+4)2+(y−4)2=(5√5)2

The centre is (−4,4) and the radius is 5√5
Graph

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