hungkaku112

Bài 2:

11+x+xy+11+y+yz+11+z+xz=111+x+xy+11+y+yz+11+z+xz=1

⇒zz+xz+1+xzxz+z+1+

1

1

+z+xz

=

1

⇒zz+xz+1+xzxz+z+1+11+z+xz=1           

⇒z+xz+1z+xz+

1

=1

⇒z+xz+1z+xz+1=1

11+x+xy+11+y+yz+11+z+xz=111+x+xy+11+y+yz+11+z+xz=1
⇒zz+xz+1+xzxz+z+1+11+z+xz=1⇒zz+xz+1+xzxz+z+1+11+z+xz=1
⇒z+xz+1z+xz+1=1⇒z+xz+1z+xz+1=1

mình chưa hiểu cái suy ra đầu tiên

+x+xy+11+y+yz+11+z+xz=111+x+xy+11+y+yz+11+z+xz=1
⇒zz+xz+1+xzxz+z+1+11+z+xz=1⇒zz+xz+1+xzxz+z+1+11+z+xz=1

Bài 2:
$\frac{1}{1+x+xy} + \frac{1}{1+y+yz} + \frac{1}{1+z+xz} = 1$
$\Rightarrow \frac{z}{z+xz+1} + \frac{xz}{xz+z+1} + \frac{1}{1+z+xz} = 1$
$\Rightarrow \frac{z+xz+1}{z+xz+1}=1$     

    

mình chưa hiểu vì sao suy ra được $\Rightarrow \frac{z}{z+xz+1} + \frac{xz}{xz+z+1} + \frac{1}{1+z+xz} = 1$