Решите уравнение: (3x+1)^2-9(x+1)(x-1)=0.

\[(3x + 1)^{2} - 9(x + 1)(x - 1) = 0\]

\[9x^{2} + 6x + 1 - 9\left( x^{2} - 1 \right) = 0\]

\[9x^{2} + 6x + 1 - 9x^{2} + 9 = 0\]

\[6x = - 10\]

\[x = - \frac{10}{6} = - 1\frac{4}{6}\]

\[x = - 1\frac{2}{3}.\]