Помогите пожалуйста с 1 номером )

Решите задачу:

$1) \frac{y-4}{3y-3}+ \frac{1}{y-1}= \frac{y-4}{3(y-1)}+ \frac{1}{y-1}= \frac{y-4+3}{3(y-1)}= \frac{(y-1)}{3(y-1)}= \frac{1}{3}$

$2) \frac{1}{3}: \frac{y+1}{3}= \frac{1*3}{3*(y+1)}= \frac{1}{(y+1)}$

$3) \frac{1}{y+1}+ \frac{2}{ y^{2}-1}= \frac{1}{y+1}+ \frac{2}{(y-1)(y+1)}= \frac{y-1+2}{(y-1)(y+1)}= \frac{(y+1)}{(y-1)(y+1)}= \frac{1}{y-1}$