б) (\frac{5x+y}{x-5y}+ \frac{5x-y}{x+5y}):-

б)

$$(\frac{5x+y}{x-5y}+ \frac{5x-y}{x+5y}) = \frac{(5x+y)(x+5y) + (5x-y)(x-5y)}{(x-5y)(x+5y)} = \frac{5x^2 + 25xy + xy + 5y^2 + 5x^2 - 25xy - xy + 5y^2}{x^2-25y^2} = \frac{10x^2+10y^2}{x^2-25y^2} = \frac{10(x^2+y^2)}{x^2-25y^2}$$.

Ответ: $$\frac{10(x^2+y^2)}{x^2-25y^2}$$