Question

Viết B = 4+\(2^2\)+\(2^3\)+\(2^4\)+..............+\(2^{20}\) dưới dạng lũy thừ với cơ số 2.

GIÚP MÌNH VỚI!!!

Answer 1

\(\Rightarrow2B=8+2^3+2^4+...+2^{21}\\ \Rightarrow2B-B=2^{21}+8-4-2^2=2^{21}\)

Answer 2

\(\Rightarrow B=2^2+2^2+2^3+2^4+...+2^{20}\)

\(\Rightarrow B=2^3+2^3+2^4+...+2^{20}\)

\(\Rightarrow B=2^4+2^4+...+2^{20}\)

\(...........\)

\(\Rightarrow B=2^{21}\)

Answer 3

B=2\(^1\)+2\(^{^{ }2}\)+2\(^3\)+2\(^4\)+..........\(2^{20}\)

2B= 2.(2\(^1\)+\(2^2\)+\(2^3\)\(2^4\)+.......\(2^{20}\))

2B=2\(^2\)+\(2^3\)+\(2^4\)+.....\(2^{20}\)+2\(^{21}\)

2B-B=2\(^{21}\)-2\(^1\)

B=\(2^{21}\)-2

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