计算(1+19\39×1)+(1+19\39×2)+(1+19\39×3)+……+(1+19\39×12用简便方法计算,

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计算(1+19\39×1)+(1+19\39×2)+(1+19\39×3)+……+(1+19\39×12用简便方法计算,

计算(1+19\39×1)+(1+19\39×2)+(1+19\39×3)+……+(1+19\39×12用简便方法计算,
计算(1+19\39×1)+(1+19\39×2)+(1+19\39×3)+……+(1+19\39×12用简便方法计算,

计算(1+19\39×1)+(1+19\39×2)+(1+19\39×3)+……+(1+19\39×12用简便方法计算,
原式=12*1+19/39*(1+2+……+12)=12=19/39*12(12+1)/2=50