Решение
[(a + 5b)/(a² - 5ab) - (a - 5b)/(a²+ 5ab)] : [(10b²)/(25b² - a²)] =
1) [(a + 5b)² - (a - 5b)²] / (a² - 25b²) =
= (a² + 10ab + 25b² - a² + 10ab - 25b²)/(a² - 25b²) = (20ab)/(a² - 25b²)
2) [(20ab)/(a² - 25b²) : [(10b²)/(25b² - a²)] =
= [ - (20ab)*(a² - 25b²)] / [(10b²)*(a² - 25b²)] = - 2a / b