6. Ответ: 3) 1, 3, 5, 7, ...
7. b/c-(b²+c²)/(bc)-c/b=(b²-b²-c²-c²)/(bc)=-2c²/(bc)=-2c/b=-2*0,9/(-4)=0,45.
x/(x-3)^2 - (x+5)/(x-3)(x+5);
(x*(x+5)-(x+5)(x-3))/(x-3)^2(x+5);
(x^2+5x-x^2+3x-5x+15)/((x-3)^2(x+5);
(3x+15)/((x-3)^2(x+5));
3(x+5)/((x-3)^2(x+5));
3/(x-3)^2
(n+2)!(n^2-9)/(n+4)!= (n+2)!(n^2-9)/((n+2)!(n+3)(n+4))=(n^2-9)/((n+3)(n+4))=
=(n^2-9)/(n^2+7n+12)=(n^2+7n+12-7n-21)/(n^2+7n+12)=1 - (7n+21)/(n^2+7n+12)
Х²=2х-1
у=х²— парабола, ветви вверх
у=2х-1—прямая
(Рисуем график функции..ищим точку пересечения)