(3 * х + 2) * (3 * х - 4) = (2 * х + 3) * (3 * х - 1) + (3 * х + 1) * (х - 4);

Раскроем скобки.

9 * x² - 12 * x + 6 * x - 8 = 6 * x² - 2 * x + 9 * x - 3 + 3 * x² - 12 * x + x - 4;

-6 * x - 8 = 7 * x - 3 - 11 * x - 4;

-6 * x - 8 = -4 * x - 7;

-6 * x + 4 * x = -7 + 8;

-2 * x = 1;

x = -1/2.