9 14 x 2 15 July 8, 2019 16 32 64 128 20 x 14 9 2x 2 15x 20 x 14 ≤ 9 2x 2 15x 2 9 x 14 15 x (- 9 10 Tính 9 14 x 7 2 x 8 15 9 14 x 7 2 x 8 15 9 × 14