Toán Lớp 6: M= 2+2^2+2^3+2^4……+2^2017+2^2018
A, tính M
B, chứng tỏ M chia hết cho 3
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Toán Lớp 6: M= 2+2^2+2^3+2^4……+2^2017+2^2018
A, tính M
B, chứng tỏ M chia hết cho 3
Comments ( 2 )
2M-M=(2^2+2^3+2^4+…+2^2018+2^2019)-(2+2^2+2^3+…+2^2017+2^2018)
M=2^2019-2
B, Ta có:
M=2+2^2+2^3+…+2^2017+2^2018
= 2.(1+2)+2^3.(1+2)+…+2^2017.(1+2)
= 2.3+2^3.3+…+2^2017.3
= 3.(2+2^3+…+2^2017) chia hết cho 3