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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: Tinh Nhanh 1990 x 1990 – 1992 x 1998

Toán Lớp 6: Tinh Nhanh
1990 x 1990 – 1992 x 1998

Comments ( 2 )

  1. 1990 × 1990 – 1992 × 1998
    = 1990 × 1990 – (1990 + 2) × 1998
    = 1990 × 1990 – 1990 × 1998 – 1998 × 2
    = 1990 × (1990 – 1998) – (1990 + 8) × 2
    = 1990 × (-8) – 1990 × 2 – 8 × 2
    = 1990 × (-8 – 2) – 16
    = 1990 × (-10) – 16
    = -19900 + 16
    = -19916
    (Giải đáp này mình check bằng máy tính rồi nha)
     

  2. 1990 × 1990 – 1992 × 1998
    =1990 × 1990 – (1990 + 2) × 1998
    =1990 × 1990 – 1990 × 1998 – 1998 × 2
    =1990 × (1990 – 1998) – (1990 + 8) × 2
    =1990 ×  (-8) – 1990 × 2 – 8 × 2
    =1990 × {(-8) – 2} – 16
    =(-19900) – 16
    =-19916

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222-9+11+12:2*14+14 = ? ( )