help !!! 4y^2 - 36y + 81 = 0 then Y should be ??

(2y - 9)(2y - 9) = 0
y = 9/2

(2y-9)^2=0
2y-9=0
y=4.5

4y^2 - 36y + 81 = 0
(2y - 9)(2y - 9) = 0

2y - 9 = 0
2y = 9
y = 9/2
y = 4 1/2 (4.5)

∴ y = 4 1/2 (4.5)

My genius calculator concedes with the first guy :P