Ответ:

  1. \(\sqrt{a-b}=\sqrt{-0.29-(-0.78)}=\sqrt{0.49}=0.7\).
  2. \(\sqrt{a-b}=\sqrt{\frac14-\left(-\frac49\right)}=\sqrt{\frac14+\frac49}=\sqrt{\frac{25}{36}}=\frac56\).

Ответ: 1) 0,7; 2) \(\frac56\).