\[ x^2 + 2x + 1 = 1 - 2x + x^2 \]
\[ x^2 + 2x + 1 - 1 + 2x - x^2 = 0 \]
\[ 4x = 0 \]
\[ x = \frac{0}{4} = 0 \]
Ответ: 0