Giải thích các bước giải:
Ta có :
$A=\dfrac{x}{xy+x+1}+\dfrac{y}{yz+y+1}+\dfrac{z}{xz+z+1}$
$\to A=\dfrac{x}{xy+x+1}+\dfrac{xy}{xyz+xy+x}+\dfrac{xyz}{xzxy+zxy+xy}$
$\to A=\dfrac{x}{xy+x+1}+\dfrac{xy}{1+xy+x}+\dfrac{1}{x+1+xy}$
$\to A=\dfrac{xy+x+1}{xy+x+1}=1$