câu 1:tính A=1+2^2+2^4+2^6+…….+2^100

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1. Bạn tham khảo :

   $A =1+2^2+2^4+2^6+…….+2^{100}$

   $2^2A = 2^2+2^4+2^6+2^8 + … +2^{102}$

   $4A -A = (2^2+2^4+2^6+2^8 + … +2^{102}) – (1+2^2+2^4+2^6+…….+2^{100})$

   $3A = 2^{102} -1$

   $A = \dfrac{2^{102}-1}{3}$

    

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