Answer:
x = - 2
Step-by-step explanation:
The equation of a circle in standard form is
(x - h)² + (y - k)² = r²
where (h, k) are the coordinates of the centre and r is the radius
To obtain this form use the method of completing the square
Given
x² + y² + 4x - 6y = b ( collect x and y terms together )
x² + 4x + y² - 6y = b
add ( half the coefficient of x/ y terms )² to both sides
x² + 2(2)x + 4 + y² + 2(- 3)y + 9 = b + 4 + 9
(x + 2)² + (y - 3)² = b + 13 ← in standard form
with (h, k) = (- 2, 3)
Thus x- coordinate of centre is x = - 2
