3 + 3/5 + 3/25 + 3/125 + 3/625
= 1875/625 + 375/625 + 75/625 + 15/625 + 3/625
= 2250/625 + 90/625 + 3/625
= 2340/625 + 3/625
= 2343/625
Bạn ơi đây là tính nhanh mà hic
sorry bạn rất nhìu
mong bạn thông cảm nếu sai mong bạn bỏ qua cho mình! :(
Đặt: \(T=3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}+\frac{3}{625}\)
\(\Rightarrow5T=5.\left(3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}+\frac{3}{625}\right)\)
\(\Rightarrow5T=15+3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}\)
\(\Rightarrow5T-T=15+3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}-\left(3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}+\frac{3}{625}\right)\)
\(\Rightarrow4T=15+3+\frac{3}{5}+\frac{3}{25}+\frac{3}{125}-3-\frac{3}{5}-\frac{3}{25}-\frac{3}{125}-\frac{3}{625}\)
\(\Rightarrow4T=15-\frac{3}{625}\)
\(\Rightarrow T=\left(15-\frac{3}{625}\right):4\)
