A2 + A + 1 + A2 − A + 1 ≥ 2 ∀ A ∈ R−=21XY

1) - DE THI MON TOAN THAM KHAO
DE THI MON TOAN THAM KHAO

1) Chứng minh rằng: a

2

+ a + 1 + a

2

− a + 1 ≥ 2 ∀ a ∈ R

−

=

2

1

x

y