bạn ơi bạn viết đề rõ ràng ra được không :) bạn viết khó hiểu quá, mình đọc không đc
Bài làm:
Ta có: \(\frac{3}{2.4.6}+\frac{3}{4.6.8}+...+\frac{3}{22.24.26}\)
\(=\frac{3}{4}\left(\frac{4}{2.4.6}+\frac{4}{4.6.8}+...+\frac{4}{22.24.26}\right)\)
\(=\frac{3}{4}\left(\frac{6-2}{2.4.6}+\frac{8-4}{4.6.8}+...+\frac{26-22}{22.24.26}\right)\)
\(=\frac{3}{4}\left(\frac{1}{2.4}-\frac{1}{4.6}+\frac{1}{4.6}-\frac{1}{6.8}+...+\frac{1}{22.24}-\frac{1}{24.26}\right)\)
\(=\frac{3}{4}\left(\frac{1}{8}-\frac{1}{624}\right)\)
\(=\frac{3}{4}.\frac{77}{624}\)
\(=\frac{77}{832}\)
Dấu (.) là dấu nhân nhé.
\(\frac{3}{2.4.6}+\frac{3}{4.6.8}+...+\frac{3}{22.24.26}\)
\(=\frac{3}{4}.\left(\frac{4}{2.4.6}+\frac{4}{4.6.8}+...+\frac{4}{22.24.26}\right)=\frac{3}{4}.\left(\frac{1}{2.4}-\frac{1}{4.6}+\frac{1}{4.6}-\frac{1}{6.8}+..+\frac{1}{22.24}-\frac{1}{24.26}\right)\)
\(=\frac{3}{4}.\left(\frac{1}{2.4}-\frac{1}{24.26}\right)=\frac{3}{4}.\left(\frac{1}{8}-\frac{1}{624}\right)=\frac{3}{4}.\frac{77}{624}=\frac{77}{832}\)
P/S : Dấu "." là dấu nhân
Ta có: \(\frac{3}{2.4.6}+\frac{3}{4.6.8}+...+\frac{3}{22.24.26}\)
\(=\frac{3}{4}\times\left(\frac{4}{2.4.6}+\frac{4}{4.6.8}+...+\frac{4}{22.24.26}\right)\)
\(=\frac{3}{4}\times\left(\frac{1}{2.4}-\frac{1}{4.6}+\frac{1}{4.6}-\frac{1}{6.8}+...+\frac{1}{22.24}-\frac{1}{24.26}\right)\)
\(=\frac{3}{4}\times\left(\frac{1}{2.4}-\frac{1}{24.26}\right)\)
\(=\frac{3}{4}\times\frac{6.13-1}{24.26}\)
\(=\frac{1}{4}\times\frac{77}{208}\)
\(=\frac{77}{832}\)
#%$#$ ^_^ chúc bn hok tốt ^_^ %#@$#
