Cho biếu thức P=10x/(x^2+2x+4)-(2x-3)/(x+4)+(x+1)/(1-x)

* Hướng dẫn giải

$$\begin{gathered} ĐK: \left\{\begin{array}{l}{x}^2+3x-4\ne 0\\ x+4\ne 0\\ 1-x\ne 0\end{array}\Rightarrow \right.\left\{\begin{array}{l}x\ne 1\\ x\ne -4\end{array}\right. \\ P=\frac{10x-(2x-3)(x-1)-(x+1)(x+4)}{(x-1)(x+4)} \\ =\frac{-3x^2+10x-7}{(x-1)(x+\_4)} \\ =\frac{-3x+7}{x+4} \end{gathered}$$

Đáp án C