Thực hiện các phép tính sau: a) 1/ x+ 2/ x+1+ 3/ x+2- 1/ x- 2/ x-1- 3/ x+2 ;

Trả lời

a, $$\begin{gathered} \frac{1}{x}+\frac{2}{x+1}+\frac{3}{x+2}-\frac{1}{x}-\frac{2}{x-1}-\frac{3}{x+2} \\ =\left(\frac{1}{x}-\frac{1}{x}\right)+\left(\frac{2}{x+1}-\frac{2}{x-1}\right)+\left(\frac{3}{x+2}-\frac{3}{x+2}\right) \end{gathered}$$

$0+\frac{2(x-1)-2(x+1)}{(x-1)(x+1)}+0=\frac{-4}{(x+1)(x-1)}=\frac{-4}{x^2-1}$