\[ 5x^2 - 11x - 9 - (3x^2 - 11x + 9) = 0 \]
\[ 5x^2 - 11x - 9 - 3x^2 + 11x - 9 = 0 \]
\[ (5x^2 - 3x^2) + (-11x + 11x) + (-9 - 9) = 0 \]
\[ 2x^2 - 18 = 0 \]
\[ 2x^2 = 18 \]
\[ x^2 = \frac{18}{2} \]
\[ x^2 = 9 \]
\[ x = \pm \sqrt{9} \]
\[ x_1 = 3, \quad x_2 = -3 \]
Ответ: x = 3, x = -3