Ответ:

  1. \(7ab+7ac=7a(b+c)\);
  2. \(5mn-5m=5m(n-1)\);
  3. \(4ax+8a=4a(x+2)\);
  4. \(6ab-3bc=3b(2a-c)\);
  5. \(-15ax-20ay=-5a(3x+4y)\);
  6. \(-2mn-4n=-2n(m+2)\).