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

Toán Lớp 8: Tính S = 3.6 + 6.9 + 9.12 + … + 150.153 Giúp mình nha .

Toán Lớp 8: Tính S = 3.6 + 6.9 + 9.12 + … + 150.153
Giúp mình nha .

Comments ( 2 )

  1. S = 3 . 6 + 6 . 9 + 9 . 12 + …. + 150 . 153
    9S = 3 . 6 . 9 + 6 . 9 . 9 + 9 . 12 . 9 + …. + 150 . 153 . 9
    9S = 3 . 6 . 9 + 6 . 9 . ( 12 – 3 ) + 9 . 12 . ( 15 – 6 ) + …. + 150 . 153 . ( 156 – 147 )
    9S = 3 . 6 . 9 + 6 . 9 . 12 – 3 . 6 . 9 + 9 . 12 . 15 – 6 . 9 . 12 + …. + 150 . 153 . 156 – 147 . 150 . 153
    9S = 150 . 153 . 156
    S = 150 . 153 . 156 : 9
    S = 150 . 156 . 17
    S = 397800

  2. Giải đáp:
    S=3.6+6.9+9.12+…..+150.153
    =>9S=3.6.9+6.9.9+9.12.9+…..+150.153.9
    =>9S=3.6.9+6.9.(12-3)+9.12.(15-6)+…..+150.153.(156-147)
    =>9S=3.6.9+6.9.12-3.6.9+9.12.15-6.9.12+…+150.153.156-148.150.153
    =>9S=150.153.156
    =>9S=50.3.51.3.156
    =>S=50.51.156

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