Б) (((a-5)(a+5)+15)/(a+5))*((a+5)²)/(a²-10) = ((a²+5a-5a-25+15)*(a+5))/(a²-10) = ((a²-10)*(a+5))/(a²-10) = a+5
в) 1/(a-1) -1/(a²-a) = (a-1)/(a(a-1)) = 1/a
4a/(a²-4)*1/a = 4/(a²-4)
1/(a-2) - 4/((a-2)(a+2)) = (a+2-4)/((a-2)(a+2)) = (a-2)/((a-2)(a+2)) = 1/(a+2)