Question

Can anyone help me identify the center & radius pls

Answer 1

see explanation

Explanation:

the equation of a circle centred at the origin is

x² + y² = r² ( r is the radius )

(11)

- 81 + x² = - y² ( add y² to both sides )

- 81 + x² + y² = 0 ( add 81 to both sides )

x² + y² = 81 ← in standard form

with centre = (0, 0 ) and r =
`√(81)` = 9

(12)

y² + x² - 196 = 0 ( add 196 to both sides )

x² + y² = 196 ← in standard form

with centre = (0, 0 ) and r =
`√(196)` = 14