Question

B= 4+4 mũ 3+4 mũ 5+.......+4 mũ 49
juppp iiiiii

Answer 1

Tính tổng hay gì bạn

Answer 2

\(B=4+4^3+4^5+...+4^{49}\)

\(4^2.B=4^2.\left(4+4^3+...+4^{49}\right)\)

\(16B=4^3+4^5+...+4^{49}\)

\(\Rightarrow16B-B=\left(4^3+4^5+...+4^{51}\right)-\left(4+4^3+...+4^{49}\right)\)

\(\Rightarrow15B=4^{51}-4\)

\(\Rightarrow B=\dfrac{4}{15}.\left(4^{50}-1\right)\)

Vậy \(B=\dfrac{4}{15}.\left(4^{50}-1\right)\)

Answer 3

`B = 4 + 4^3 + 4^5 + ... + 4^49`

`=> 16B = 4^3 + 4^5 + 4^7 + ... + 4^51`

`-`

 `B    = 4 + 4^3 + 4^5 + ... + 4^49`

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`=> 15B  =  4^51 - 4`

`=>     B   = (4^51 - 4)/15`