4/15+ 4/35+ 4/63+ 4/99=16/33
chúc bạn hok tốt
\(\frac{4}{12}+\frac{4}{35}+\frac{4}{63}+\frac{4}{99}\)
\(=2.\left(\frac{2}{12}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}\right)\)
\(=2.\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right)\)
\(=2.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)
\(=2.\left(\frac{1}{3}-\frac{1}{11}\right)\)
\(=2.\left(\frac{11}{33}-\frac{3}{33}\right)\)
\(=2.\frac{8}{33}\)
\(=\frac{16}{33}\)
Tham khảo nhé~
\(\frac{4}{15}+\frac{4}{35}+\frac{4}{63}+\frac{4}{99}\)
\(=4\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}\right)\)
\(=4\left(\frac{2}{21}+\frac{1}{63}+\frac{1}{99}\right)\)
\(=4\left(\frac{1}{9}+\frac{1}{99}\right)\)
\(=4\cdot\frac{4}{33}=\frac{16}{33}\)
4/15+4/35+4/63+4/99= 2x(2/3x5+2/5x7+2/7x9+2/9x11)
=2x(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)=2x(1/3-1/11)=16/33
\(\frac{4}{15}+\frac{4}{35}+\frac{4}{63}+\frac{4}{99}\)
\(=2(\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99})\)
\(=2(\frac{2}{3\times5}+\frac{2}{5\times7}+\frac{2}{7\times9}+\frac{2}{9\times11})\)
\(=2(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11})\)
\(=2(\frac{1}{3}-\frac{1}{11})\)
\(=2\times\frac{8}{33}\)
\(=\frac{16}{33}\)
\(\frac{4}{15}+\frac{4}{35}+\frac{4}{63}+\frac{4}{99}\)
\(=\frac{4}{3.5}+\frac{4}{5.7}+\frac{4}{7.9}+\frac{4}{9.11}\)
\(=\frac{4}{2}.\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right)\)
\(=2.\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)
\(=2.\left(\frac{1}{3}-\frac{1}{11}\right)\)
\(=2.\left(\frac{11}{33}-\frac{3}{33}\right)\)
\(=2.\frac{8}{33}\)
\(=\frac{2.8}{33}\)
\(=\frac{16}{33}\)