Упростите выражение: (a-1)/(3a^2+6a+3)-1/(2a+2).

\[\frac{a - 1}{3a^{2} + 6a + 3} - \frac{1}{2a + 2} =\]

\[= \frac{a - 1^{\backslash 2}}{3 \cdot (a + 1)^{2}} - \frac{1^{\backslash 3(a + 1)}}{2 \cdot (a + 1)} =\]

\[= \frac{2a - 2 - 3a - 3}{6 \cdot (a + 1)^{2}} =\]

\[= \frac{- a - 5}{6 \cdot (a + 1)²} = - \frac{a + 5}{6 \cdot (a + 1)²}\]