(2x - 1)(2x + 1) - 4(x + 5)² = 19;

4x^2 - 1 - 4(x^2 + 10x + 25) = 19;

4x^2 - 1 - 4x^2 - 40x - 100 = 19;

4x^2 - 4x^2 - 40x = 19 + 100 + 1;

-40x = 120;

x = 120 : (-40);

x = -3.