What the solution of the equation: y^2-3y=9 ?

y^2-3y=9

y^2 - 3y = 9
complete the square
y^2 - 3y + 9/4 = 9 + 9/4
(y - 3/2)^2 = 45/4

+- (y - 3/2) = 45/4

solve for y
y = 3/2 (sqrt5 + 1)
y = -3/2 (-1 + sqrt5)