Toán Lớp 7: Tính
B=1+3^3+3^4+….+3^2016+3^2019
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Toán Lớp 7: Tính
B=1+3^3+3^4+….+3^2016+3^2019
Comments ( 2 )
3^3B=3^3+3^4+3^5+……….+3^2017+3^2020
3^3B-B=27B-B=(3^3+3^4+3^5+……….+3^2017+3^2020)-(1+3^3+3^4+….+3^2016+3^2019)
26B=3^2020-1
B=(3^2020-1)/26