The center of a circle is at (7, -3) and it has a radius of 9. What is the equation of the circle?
The standard form of the equation of a circle is
#(x - a )^2 + (y - b )^2 = r^2 #
where (a , b ) are the coords of centre and r , the radius
here (a , b ) = (7 , -3 ) and r = 9. Substituting into standard equation gives
# (x - 7 )^2 + (y + 3 )^2 = 81#