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Aflati x din egalitatile
a)1+2+2²+2³+...+2ˣ=2⁷⁵-1


Răspuns :

S=2^x+2^(x-1)+2^(x-2)+..............2+1
2S=2^(x+1) +2^x+2^(x-1)+..........2^2+2
2S-S=2^(x+1) - 1
S=2^(x+1) - 1
2^(x+1) - 1=2^75 - 1
2^(x+1)=2^75
x+1=75
x=74
2+2^2+2^3+2^4+…+2^x+2^(x+1) - 1+2+2^2+2^3+…+2^x 1+2+2^2+…+2^x=2^(x+1)-1=>2^(x+1)-1=2^75-1 x+1=75 x=74