sqrt(2y-1) = 2 + sqrt(y-4)
( sqrt(2y-1))^2 = (2+sqrt(y-4))^2
2y-1 = 4 + 4sqrt(y-4) + y - 4
y-1 = 4sqrt(y-4)
(y-1)^2 = (4sqrt(y-4))^2
y^2 - 2y + 1 = 16(y-4)
y^2 - 2y + 1 = 16y - 64
y^2 - 18y + 65 = 0
A = 1, B = - 18 and C = 65
C = 65 = -3*( - 15)
-3 - 15 = - 18 = B, and
y^2 - 18y + 65 =0 = (y-3)(y- 15)
y-3 = 0 and y - 15 = 0
y = 3 and y = 15