Khai triển (a + b + c)^2; (a + b − c)^2; (a − b − c)^2.
Khai triển (a + b + c)2; (a + b − c)2; (a − b − c)2.
+) (a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ca
+) (a + b − c)2 = a2 + b2 + c2 + 2ab − 2bc − 2ca
+) (a − b − c)2 = a2 + b2 + c2 − 2ab + 2bc − 2ca.