Factorise by grouping method:
a2+b−ab−a
a2+b−ab−a=a2−ab+b−a=a(a−b)−(a−b)=(a−b)(a−1)
a2+4b2−3a+6b−4ab
y2−(a+b)y+ab
ab−2b+a2−2a
(2a−b)2−10a+5b
16(a+b)2−4a−4b