Explain how you know the origin is the centre of the circle defined by the equation x2+y2=45.

X² + y² = 45

x² - x² + y² = 45 - x²

y² = 45 - x²

y = 3√ (5) - x

x² + (3√ (5) - x) ² = 45

x² + 45 - x² = 45

x² - x² + 45 = 45

0x² + 45 = 45

-45 - 45

0x² = 0

0 0

x² = 0

x = 0

(0) ² + y² = 45

0 + y² = 45

-0 - 0

y² = 45

y = 3√5

(x y) = (0, 3√5)