Answer:
71
Explanation:
the circle standard form is
(x - h)² + (y - k)² = r²
r being the radius, (h, k) being the coordinates of the center.
fully multiplied that is
x² - 2hx + h² + y² - 2ky + k² = r²
we have here
4x² + 12x + 4y² - 40y - B = 0
our first step is to bring this back to an excision in x² and y². so, we divide everything by 4.
x² + 3x + y² - 10y - B/4 = 0
by comparing this to the general equation we see
3 = -2h
h = -3/2 = -1.5
-10 = - 2k
k = 5
-B/4 = h² + k² - r² = 9/4 + 25 - (3×sqrt(5))² =
= 9/4 + 25 - 9×5 = 9/4 + 25 - 45 = 9/4 - 20
-B = 9 - 80 = -71
B = 71