1) 12ab - 18b² = 6b(2a - 3b)
2) 21x7 - 7x4 = 7x4(3x³ - 1)
3) 8x - 8y + ax - ay = 8(x-y) + a(x-y) = (x-y)(8+a)
Ответ: 1) 6b(2a - 3b); 2) 7x4(3x³ - 1); 3) (x-y)(8+a)