Ответ:

  1. \(1-\frac a5-\frac b4=\frac{20-4a-5b}{20}\).
  2. \(12-\frac1a-\frac1b=\frac{12ab-a-b}{ab}\).
  3. \(\frac{a-2}{2}-1-\frac{a-3}{3}=\frac{a-6}{6}\).
  4. \(4a-\frac{a-1}{4}-\frac{a+2}{3}=\frac{41a-5}{12}\).
  5. \(\frac{a+b}{4}-a+b=\frac{-3a+5b}{4}\).
  6. \(a+b-\frac{a^2+b^2}{a}=\frac{ab-b^2}{a}\).

Ответ: а) \(\frac{20-4a-5b}{20}\); б) \(\frac{12ab-a-b}{ab}\); в) \(\frac{a-6}{6}\); г) \(\frac{41a-5}{12}\); д) \(\frac{-3a+5b}{4}\); е) \(\frac{ab-b^2}{a}\).