Răspuns :
Obs. Folosim formula (a+b+c)² = a²+b²+c²+2ab+2bc+2ac
(x - 2y - 3z)² =
= x² + 4y² + 9z² - 4xy + 12yz - 6xz
(2x - 3y - 5z)² =
= 4x² + 9y² + 25z² - 12xy + 30yz - 20xz
(x - 2y - 3z)² =
= x² + 4y² + 9z² - 4xy + 12yz - 6xz
(2x - 3y - 5z)² =
= 4x² + 9y² + 25z² - 12xy + 30yz - 20xz