2. Представьте в виде дроби: a) $$rac{y-20}{4y} + \frac{5y-2}{y^2}$$; б) $$rac{1}{5c-d} - \frac{1}{5c+d}$$; в) $$rac{7}{a+5} - \frac{7a-3}{a^2+5a}$$.

a) $$rac{y-20}{4y} + \frac{5y-2}{y^2} = \frac{(y-20)y}{4y^2} + \frac{4(5y-2)}{4y^2} = \frac{y^2 - 20y + 20y - 8}{4y^2} = \frac{y^2-8}{4y^2}$$ б) $$rac{1}{5c-d} - \frac{1}{5c+d} = \frac{5c+d}{(5c-d)(5c+d)} - \frac{5c-d}{(5c-d)(5c+d)} = \frac{5c+d - (5c-d)}{(5c)^2 - d^2} = \frac{5c+d - 5c + d}{25c^2 - d^2} = \frac{2d}{25c^2 - d^2}$$ в) $$rac{7}{a+5} - \frac{7a-3}{a^2+5a} = \frac{7}{a+5} - \frac{7a-3}{a(a+5)} = \frac{7a}{a(a+5)} - \frac{7a-3}{a(a+5)} = \frac{7a - (7a-3)}{a(a+5)} = \frac{7a - 7a + 3}{a(a+5)} = \frac{3}{a(a+5)}$$