Đáp án+gải thích các bước giải:
a)
$MTC=x^2= (x-1)(x+1)$
Ta có:
$\dfrac{x-1}{x+1}=\dfrac{(x-1).(x-1)}{(x+1)(x-1)}=\dfrac{(x-1)^2}{(x-1)(x+1}$
$\dfrac{x+1}{x-1}=\dfrac{(x+1).(x+1)}{(x-1)(x+1)}=\dfrac{(x+1)^2}{(x-1)(x+1)}$
$\dfrac{1}{x^2-1}=\dfrac{1}{x^2-1^2}=\dfrac{1}{(x-1)(x+1)}$