Объяснение:

[tex] \frac{{x}^{2} - {y}^{2} - {z}^{2} + 2yz }{ {y}^{2} - {x}^{2} - {z}^{2} - 2xz} = \frac{ {x}^{2} - ( {y}^{2} - 2yz + {z}^{2} ) }{ {y}^{2} - ( {x}^{2} + 2xz + {z)}^{2} } = \frac{ {x}^{2} - (y - z{)}^{2} }{ {y}^{2} - (x + z {)}^{2} } = [/tex]

[tex] = \frac{(x - y + z)(x + y - z)}{(y - x - z)(y + x + z)} = \frac{ - x - y + z}{y + x + z} [/tex]