Ответ:

  1. \(\frac{8}{x+6}-\frac{8}{x-7}=\frac{8(x-7)-8(x+6)}{(x+6)(x-7)}=\frac{-104}{(x+6)(x-7)}\).
  2. \(y-3a=-(3a-y)\), сондықтан \(\frac{9a^2+y^2}{3a-y}-\frac{6ay}{3a-y}=\frac{9a^2-6ay+y^2}{3a-y}=3a-y\).
  3. \(by-a=-(a-by)\), сондықтан \(\frac{ay}{a-by}-\frac{3a-by}{a-by}=\frac{ay-3a+by}{a-by}=\frac{y(a+b)-3a}{a-by}\).
  4. \(6y-ax=-(ax-6y)\), сондықтан \(\frac{a^2x^2+36y^2-12axy}{ax-6y}=\frac{(ax-6y)^2}{ax-6y}=ax-6y\).

Жауап: 1) \(-\frac{104}{(x+6)(x-7)}\); 2) \(3a-y\); 3) \(\frac{y(a+b)-3a}{a-by}\); 4) \(ax-6y\).