Toán Lớp 6: Tính A = $\begin{cases} \\\\ \end{cases}$ 1/2+1/2^2+1/2^3+…….+1/2^2019 $\left.\begin{matrix} \\\\ \end{matrix}\right\}$ : $\begin{cases} \\\\ \end{cases}$ 1-1/2^2019$\left.\begin{matrix} \\\\ \end{matrix}\right\}$
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Toán Lớp 6: Tính A = $\begin{cases} \\\\ \end{cases}$ 1/2+1/2^2+1/2^3+…….+1/2^2019 $\left.\begin{matrix} \\\\ \end{matrix}\right\}$ : $\begin{cases} \\\\ \end{cases}$ 1-1/2^2019$\left.\begin{matrix} \\\\ \end{matrix}\right\}$
Comments ( 1 )
Đặt B = 1/2 + 1/2^2 + 1/2^3 + ….. + 1/2^2019
2B = 1 + 1/2 + …+ 1/ 2^2018
2B – B =(1 + 1/2+1/2^2+ …+1/2^2018) – (1/2+1/2^2+…+1/2^2019)
B = 1 – 1/ 2^2019
=> A = 1