`(a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ac` `(a – b – c)² = a² + b² + c² – 2ab – 2ac + 2bc` Bình luận
(A+B+C) ² = A²+B²+C²+2AB+2BC+2AC
(A- B- C) ² =A ²+B ²+C ² -2AB-2BC+2BC
`(a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ac`
`(a – b – c)² = a² + b² + c² – 2ab – 2ac + 2bc`