a1−b−b(1−a)1-b-b(1-a)1−b−b(1−a) = a1−b−b+ab1-b-b+ab1−b−b+ab = a1−2b+ab1-2b+ab1−2b+ab = a - 2ab + a^2b
a1−b−b(1−a)1-b-b(1-a)1−b−b(1−a) = a1−b−b+ab1-b-b+ab1−b−b+ab = a1−2b+ab1-2b+ab1−2b+ab = a - 2ab + a^2b