Answer:
centre = (4, 0 )
Explanation:
the equation of a circle in standard form is
(x - h)² + (y - k)² = r²
(h, k ) are the coordinates of the centre and r is the radius
(x - 4)² + y² = 90
or
(x - 4)² + (y - 0)² = 90 ← is in standard form
with h = 4 and k = 0
centre = (4, 0 )