A= 4 + $2^{2}$ + $2^{3}$ + $2^{4}$ +…+ $2^{20}$

1 bình luận về “A= 4 + $2^{2}$ + $2^{3}$ + $2^{4}$ +…+ $2^{20}$”

1. A=4+2²+2³+2^4+….+2^20

   A=4+(2²+2³+2^4+…..+2^10

   A-4=2²+2³+2^4+…..+2^10

   2(A-4)=2³+2^4+2^5+….+2^21

   A-4=2(A-4)-(A-4)=(2³+2^4+2^5+…+2^21)-(2²-2³+2^4+…+2^20)

   A-4=(2³-2³)+(2^4-2^4)+(2^5-2^5)+…..+(2^20-2^20)+(2^21-2²)

   A-4=2^21-4

   A=2^21-4+4

   A=2^21

   $\textit{tenchunick}

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