Tính nhanh: (500 x 9 - 250 x 18) x (1 + 2 + 3 + + 9)
Giải thích
(500 × 9 – 250 × 18) × (1 + 2 + 3 + … + 9)
= (4500 – 4500) × (1 + 2 + 3 + … + 9)
= 0 × (1 + 2 + 3 + … + 9)
= 0
(500 × 9 – 250 × 18) × (1 + 2 + 3 + … + 9)
= (4500 – 4500) × (1 + 2 + 3 + … + 9)
= 0 × (1 + 2 + 3 + … + 9)
= 0