1) 2 x^3 - x (x ^ 2 - 6) - 3 (2 x - 1) - 30 = 0; 2 * x ^ 3 - x ^ 3 + 6 * x - 6 * x + 3 - 30 = 0; x ^ 3 + 3 - 30= 0; x ^ 3 - 27 = 0; (x - 3) * (x ^ 2 + 3 * x + 9) = 0; x - 3 = 0; x = 3; 2) 12 x (x - 8) - 4 x (3 x - 5) = 10 - 26 x; 12 * x ^ 2 - 96 - 12 * x ^ 2 + 20 * x = 10 - 26 * x; - 96 + 20 * x = 10 - 26 * x; 20 * x + 26 * x = 10 + 96; 46 * x = 106; x = 106 / 46; x = 53 / 23; 3) 8(x^2-5)-5x(x+2)+10(x+4)=0; 8 * x ^ 2 - 40 - 5 * x ^ 2 - 10 * x + 10 * x + 40 = 0; 3 * x ^ 2 = 0; x ^ 2 = 0; x = 0.