2x^2 + 3x - 4 = 2x^2 + 5/(3x)
3x - 4 = 5/(3x)
9x^2 - 12x - 5 = 0
(3x - 5)* (3x + 1) = 0
所以：
3x-5 = 0 or 3x+1 = 0
解得：x1 = 5/3, x2 = -1/3