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

Toán Lớp 6: Cho 1^2+2^2+3^+…+9^2+10^2=385. Tính 2^2+4^2+…+16^2+18^2=

Toán Lớp 6: Cho 1^2+2^2+3^+…+9^2+10^2=385. Tính 2^2+4^2+…+16^2+18^2=

Comments ( 2 )

  1.  Đặt T = 1² + 2² + … + 10² = 385
    => T x 2² = 1². 2² + 2². 2² + … + 2². 10² = 385. 2²
    => T x 2² = (1. 2)² + (2. 2)² + … + (10². 2²) = 385. 2²
    => T x 2² = 2² + 4² + 20² = 385. 2²
    => T x 2² = S = 385. 2²
    => S = 385. 4 

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