Tính nhanh giá trị biểu thức:

A = (81 – 3 × 27) × (1 + 2 + 3 + 4 + … + 999)

    = (81 – 81) × (1 + 2 + 3 + 4 + … + 999)

    = 0 × (1 + 2 + 3 + 4 + … + 999)

    = 0

B = 2756 × (43 × 10 – 2 × 43 × 5)

    = 2756× (43 × 100 – 43 × 10)

    = 2756× 0

    = 0

C = (a × 7 + a × 8 – a × 15) × (293 + 97)

    = a × 0 × (293 + 97)

    = 0

D = 70 × 3 + 9 × 70 – 12 × 65 – 12 × 5

    = 70 × (3 + 9) – 12 × (65 + 5)

    = 70 × 12 – 12 × 70

    = 0