-[ ((x2)2+(y2)2+(z2)2-2x2y2-2x2z2+2y2z2)-4y2z2]
- ( (x2-y2-z2)2-(2yz)2)
-( x2-y2-z2-2yz )(x2-y2-z2+2yz)
Sai thì bảo mình đừng k sai a -)
\(=4x^2z^2-\left(x^4+y^4+z^4-2x^2y^2+2x^2z^2-2y^2z^2\right)=4x^2z^2-\left(x^2-y^2+z^2\right)^2\)
\(=\left(2xz+x^2-y^2+z^2\right)\left(2xz-x^2+y^2-z^2\right)=\left[\left(x+z\right)^2-y^2\right]\left[y^2-\left(x-z\right)^2\right]\)
\(=\left(x+y+z\right)\left(x+y-z\right)\left(y+x-z\right)\left(y-x+z\right)\)