Simplify and show:

2a-6(10a)-5a^2(2)
-----------------
(2a-6)^2

This is my work but its not right.

10a-10a^2
--------
2a-6

Then solve for a by setting numerator to zero. so I got this...

10a-10a^2=0
10a(1-a)=0
a=0, a=1

My book says a=0, or a=6 why didn't I get this?