Toán Lớp 8: Anh em nào giỏi giải hộ mình :2+2^2+2^3+2^4+…+2^2017=?
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Toán Lớp 8: Anh em nào giỏi giải hộ mình :2+2^2+2^3+2^4+…+2^2017=?
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=> 2A = 2 . ( 2 + 2^2 + 2^3 + 2^4 + … + 2^{2017} )
=> 2A = 2^2 + 2^3 + 2^4 + 2^5 + … + 2^{2018}
Mà A = 2 + 2^2 + 2^3 + 2^4 + … + 2^{2017}
=> 2A – A = ( 2^2 + 2^3 + 2^4 + 2^5 + … + 2^{2018} ) – ( 2 + 2^2 + 2^3 + 2^4 + … + 2^{2017} )
=> A = 2^{2018} – 2
Vậy : A = 2^{2018} – 2