Ответ:

  1. \(\sqrt{18x}-\sqrt{2x}+\sqrt{50x}=3\sqrt{2x}-\sqrt{2x}+5\sqrt{2x}=7\sqrt{2x}\).
  2. \(\sqrt{24}+\sqrt{54}-\sqrt{96}=2\sqrt6+3\sqrt6-4\sqrt6=\sqrt6\).
  3. \(3\sqrt{50c}-2\sqrt{18c}+\sqrt{8c}=15\sqrt{2c}-6\sqrt{2c}+2\sqrt{2c}=11\sqrt{2c}\).
  4. \((\sqrt5+2\sqrt3)^2=5+4\sqrt{15}+12=17+4\sqrt{15}\).
  5. \((\sqrt{13}-2)(\sqrt{13}+2)=13-4=9\).
  6. \((3\sqrt2-\sqrt7)(3\sqrt2+\sqrt7)=18-7=11\).

Ответ: 1) \(7\sqrt{2x}\); 2) \(\sqrt6\); 3) \(11\sqrt{2c}\); 4) \(17+4\sqrt{15}\); 5) \(9\); 6) \(11\).