3. Упростите выражение: 1) \(\frac{y+3}{2y+2} - \frac{y+1}{2y-2} + \frac{3}{y^2-1}\);

$$\frac{y+3}{2y+2} - \frac{y+1}{2y-2} + \frac{3}{y^2-1} = \frac{y+3}{2(y+1)} - \frac{y+1}{2(y-1)} + \frac{3}{(y-1)(y+1)} = \frac{(y+3)(y-1) - (y+1)(y+1) + 6}{2(y-1)(y+1)} = \frac{y^2+2y-3 - y^2-2y-1 + 6}{2(y-1)(y+1)} = \frac{2}{2(y-1)(y+1)} = \frac{1}{(y-1)(y+1)} = \frac{1}{y^2-1}$$