Factorise by grouping method:
y2−(a+b)y+ab
y2−(a+b)y+ab=y2−ay−by+ab=y(y−a)−b(y−a)=(y−a)(y−b)
a2+b−ab−a
x(6x−5y)−4(6x−5y)2
a3+a−3a2−3
a(a−4)−a+4
ab−2b+a2−2a