a, 2x(x - 5) - x(3 + 2x) = 26
2x^2 - 10x - 3x - 2x^2 = 26
-13x = 26
x = -2
Vậy x = -2
b, (2x + 1)^3 + x^3 - 2x^2 + 3x = 9x^3 + 10x^2 - 5x + 6
8x^3 + 12x^2 + 6x + 1 + x^3 - 2x^2 + 3x = 9x^3 + 10x^2 - 5x + 6
9x^3 + 10x^2 + 9x + 1 = 9x^3 + 10x^2 - 5x + 6
4x + 7 = 0
4x = -7
x = -7/4
Vậy x = -7/4
Duy gửi!