$\"\"$

Given that equation of a circle is $\"\"$ .

$\"\"$ (Equation of a circle)

$\"\"$ (Add 81 to each side) \ \

$\"\"$ (Simplify)

$\"\"$ -------(1) (Simplify) $\"\"$

The above equation is of the form $\"\"$ -------(2)

Compare the two equations(1) and (2),

Hence $\"\"$ , $\"\"$ and $\"\"$ $\"\"$

The center = $\"\"$ and $\"\"$ .