Question

Find the coordinates of the center and the measure of the diameter for a circle whose equation is (x + 8)2 + (y - 4)2 = 81

Answer 1

Reminder :

( x + a )^2 + ( y + b )^2 = ( R )^2

Center : O = ( - a , - b )

R = radius

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( x + 8 )^2 + ( y - 4 )^2 = ( 9 )^2

Center : O = ( - 8 , 4 )

radius = 9

Diameter = 2 × radius = 18