Tính nhanh: 127 × (27 ‒ 56) ‒ 27 × (127 ‒ 56).

127 × (27 ‒ 56) ‒ 27 × (127 ‒ 56)

= 127 × 27 ‒ 127 × 56 ‒ 27 × 127 + 27 × 56

= (127 × 27 ‒ 27 × 127) ‒ (127 × 56 − 27 × 56)

= 0 ‒ 56 × (127 ‒ 27)

= 0 ‒ 56 × 100

= 0 ‒ 5600

= ‒5600.