1. a) a^2 + ad - a - d = (a^2 - a) + (ad - d) = a(a - 1) + d(a -1) = (a - 1)(a+d)
b) y^3 - xy^2 + y - x = (y^3 + y) - (xy^2 + x) = y(y^2 + 1) - x(y^2 + 1) = (y^2 + 1)(y - x)
c) 3ab - b^2 + 3a^2 - ab = (3ab + 3a^2) - (b^2 + ab) = 3a(b + a) - b(b+a) = (3a - b)(b + a)
d) 6y^2 - 3y + 2ay - a = (6y^2 - 3y) + (2ay - a) = 3y(2y - 1) + a(2y - 1) = (3y + a)(2y - 1)
2. a) ax - a + bx -b + cx - c = a(x - 1) + b(x - 1) + c(x -1) = (a+b+c)(x - 1)
b) ax + bx - ay - by + az + bz = x(a+b) - y(a+b) + z(a + b) = (a + b)(x + z - y)
c) ax - bx - x + ay - by - y = x(a - b - 1) + y(a - b - 1) = (x + y)(a - b - 1)
3. b) (ax - ay - x^2 + xy) / (ax - a^2) = ( (a-x - a)(y - x)) / (a(x - a)) = (y - x) / a