Concavity

Here's my question:
Example: examine the function
Y=x(x-1)^3
Y'=3x(x-1)^2+(x-1)^3=(x-1^2(4x-1)
Y"=4(x-1)^2+2(x-1)(4x-1) ... How did they get 4(x-1)^2+2(x-1)(4x-1)?