bạn ghép 1 với 3 ; 2 với 5
sau đó quy đồng là ra mà
\(\frac{3}{4}+\frac{2}{7}+\frac{1}{4}+\frac{3}{5}+\frac{5}{7}\)
=\(\frac{3}{4}+\frac{1}{4}+\frac{2}{7}+\frac{5}{7}+\frac{3}{5}\)
=\(\frac{4}{4}+\frac{7}{7}+\frac{3}{5}\)
=1+1 +\(\frac{3}{5}\)
= 2 + \(\frac{3}{5}\)
=\(\frac{13}{5}\)
\(\frac{3}{4}+\frac{2}{7}+\frac{1}{4}+\frac{3}{5}+\frac{5}{7}\)
\(=\left(\frac{3}{4}+\frac{3}{5}\right)+\left(\frac{2}{7}+\frac{5}{7}\right)+\frac{1}{4}\)
\(=\frac{27}{20}+1+\frac{1}{4}\)
\(=\frac{13}{5}\)
\(\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{2}{7}+\frac{5}{7}\right)+\frac{3}{5}\)= \(1+1+\frac{3}{5}\)= \(2+\frac{3}{5}\)=\(\frac{10}{5}+\frac{3}{5}\)= \(\frac{13}{5}\)
\(\frac{3}{4}\)+ \(\frac{2}{7}\)+\(\frac{1}{4}\)+\(\frac{3}{5}\)+\(\frac{5}{7}\)
= \(\frac{3}{4}\)+ \(\frac{1}{4}\)+\(\frac{2}{7}\)+\(\frac{5}{7}\)+\(\frac{3}{5}\)
= 1+1+\(\frac{3}{5}\)
= 2+ \(\frac{3}{5}\)
= \(\frac{13}{5}\)