Toán Lớp 6: chứng minh A chia hết cho 4
A= 1- 3+3 ² – 3 ³+……+3 ^98-3^99
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Toán Lớp 6: chứng minh A chia hết cho 4
A= 1- 3+3 ² – 3 ³+……+3 ^98-3^99
Comments ( 2 )
Giải đáp:
A = 1 – 3 + 3^2 + 3^3 + … + 3^98 – 3^99
A = (1 + 3^1) . 3^0 + (1 + 3^1) . 3^2 + … + (1 + 3^1) . 3^98
A = 4 . 3^0 + 4 . 3^2 + … + 4 + 3^98
A = 4 . (3^0 + 3^2 + … + 3^98)
=> A \vdots 4 (đpcm)