Ответ:

  1. При a ≥ 0: \(\sqrt{4a}+\sqrt{64a}-\sqrt{9a}=2\sqrt a+8\sqrt a-3\sqrt a=7\sqrt a\).
  2. \(\sqrt{98}+\sqrt{242}-\sqrt{50}=7\sqrt2+11\sqrt2-5\sqrt2=13\sqrt2\).
  3. При c ≥ 0: \(2\sqrt{125c}-4\sqrt{80c}+\frac17\sqrt{245c}=10\sqrt{5c}-16\sqrt{5c}+\sqrt{5c}=-5\sqrt{5c}\).