Solve for y:
-y^2 + 6 y + 4 = 0
Multiply both sides by -1:
y^2 - 6 y - 4 = 0
Add 4 to both sides:
y^2 - 6 y = 4
Add 9 to both sides:
y^2 - 6 y + 9 = 13
Write the left hand side as a square:
(y - 3)^2 = 13
Take the square root of both sides:
y - 3 = sqrt(13) or y - 3 = -sqrt(13)
Add 3 to both sides:
y = 3 + sqrt(13) or y - 3 = -sqrt(13)
Add 3 to both sides:
Answer: y = 3 + sqrt(13) or y = 3 - sqrt(13)