Cho D = 5x^2/(5x - 6) + (x^2 - 1)/(6 - 5x) - (7 + x - x^2)/(5x - 6). Sau khi thu gọn

Câu hỏi :

Cho D = $\frac{{\text{5x}}^{\text{2}}}{\text{5x}-\text{6}}+\frac{{\text{x}}^{\text{2}}-\text{1}}{\text{6}-\text{5x}}-\frac{\text{7}+\text{x}-{\text{x}}^{\text{2}}}{\text{5x}-\text{6}}$ . Sau khi thu gọn hoàn toàn thì D có tử thức là?