Show that $\left\| z _ { 1 } - z _ { 2 } \right\| = \left\| z _ { 1 } + z _ { 2 } \right\|$ and that $- \left( I _ { n } + { } ^ { t } O \right) z _ { 1 } - \left( I _ { n } - { } ^ { t } O \right) z _ { 2 } = 0$.
Show that $\left\| z _ { 1 } - z _ { 2 } \right\| = \left\| z _ { 1 } + z _ { 2 } \right\|$ and that $- \left( I _ { n } + { } ^ { t } O \right) z _ { 1 } - \left( I _ { n } - { } ^ { t } O \right) z _ { 2 } = 0$.