\[(3x + 1)^{2} - 100 = 0\]
\[(3x + 1 - 10)(3x + 1 + 10) = 0\]
\[(3x - 9)(3x + 11) = 0\]
\[3x - 9 = 0\ \ \ \ \ \ \ 3x + 11 = 0\]
\[3x = 9\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 3x = - 11\]
\[x = 3\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - \frac{11}{3} = - 3\frac{2}{3}\]
\[Ответ:x = 3;\ x = - 3\frac{2}{3}.\]