Toán Lớp 6: Tìm x bằng cách nhanh nhất:
A=1+2+2^2+…+2^99
2A+1=2^x
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Toán Lớp 6: Tìm x bằng cách nhanh nhất:
A=1+2+2^2+…+2^99
2A+1=2^x
Comments ( 2 )
2A=2+2^2+2^3+…+2^100
2A-A=(2+2^2+2^3+…+2^100)-(1+2+2^2+…+2^99)
2A-A=2^100-1
=>2A-A+1=2^x
=>2^100-1+1=2^x
=>2^100=2^x
=>x=100
Vậy x=100