Ответ:

  1. \(7ax+7bx=7x(a+b)\);
  2. \(3by-6b=3b(y-2)\);
  3. \(-5mn+5n=5n(1-m)\);
  4. \(3a+9ab=3a(1+3b)\);
  5. \(5y^2-15y=5y(y-3)\);
  6. \(3x+6x^2=3x(1+2x)\);
  7. \(a^2-ab=a(a-b)\);
  8. \(8mn-4m^2=4m(2n-m)\);
  9. \(-6ab+9b^2=3b(3b-2a)\);
  10. \(x^2y-xy^2=xy(x-y)\);
  11. \(ab-a^2b=ab(1-a)\);
  12. \(-p^2q^2-pq=-pq(pq+1)\).