Ответ:

  1. \(x+\frac{1}{y}=\frac{xy+1}{y}\).
  2. \(\frac{1}{a}-a=\frac{1-a^2}{a}\).
  3. \(3a-\frac{a}{4}=\frac{12a-a}{4}=\frac{11a}{4}\).
  4. \(5b-\frac{2}{b}=\frac{5b^2-2}{b}\).
  5. \(\frac{a^2+b}{a}-a=\frac{a^2+b-a^2}{a}=\frac{b}{a}\).
  6. \(2p-\frac{4p^2+1}{2p}=\frac{4p^2-4p^2-1}{2p}=-\frac{1}{2p}\).
  7. \(\frac{(a-b)^2}{2a}+b=\frac{(a-b)^2+2ab}{2a}=\frac{a^2+b^2}{2a}\).
  8. \(c-\frac{(b+c)^2}{2b}=\frac{2bc-(b+c)^2}{2b}=-\frac{b^2+c^2}{2b}\).

Ответ: а) \(\frac{xy+1}{y}\); б) \(\frac{1-a^2}{a}\); в) \(\frac{11a}{4}\); г) \(\frac{5b^2-2}{b}\); д) \(\frac ba\); е) \(-\frac1{2p}\); ж) \(\frac{a^2+b^2}{2a}\); з) \(-\frac{b^2+c^2}{2b}\).