A=1/6+1/12+1/20+1/30+1/42+1/56 GIÚP MK VS THANKS NHIỀU 04/10/2021 Bởi Adalyn A=1/6+1/12+1/20+1/30+1/42+1/56 GIÚP MK VS THANKS NHIỀU
A=$\frac{1}{6}$ + $\frac{1}{12}$ + $\frac{1}{20}$ +$\frac{1}{30}$ +$\frac{1}{42}$ +$\frac{1}{56}$ =$\frac{1}{2.3}$ + $\frac{1}{3.4}$ + $\frac{1}{4.5}$ +$\frac{1}{5.6}$ +$\frac{1}{6.7}$ +$\frac{1}{7.8}$ =$\frac{3-2}{2.3}$ + $\frac{4-3}{3.4}$ + $\frac{5-4}{4.5}$ +$\frac{6-5}{5.6}$ +$\frac{7-6}{6.7}$ +$\frac{8-7}{7.8}$ =$\frac{1}{2}$ – $\frac{1}{3}$ + $\frac{1}{3}$- $\frac{1}{4}$+$\frac{1}{4}$ -$\frac{1}{5}$ +$\frac{1}{5}$-$\frac{1}{6}$ +$\frac{1}{6}$-$\frac{1}{7}$+$\frac{1}{7}$-$\frac{1}{8}$ =$\frac{1}{2}$ -$\frac{1}{8}$ =$\frac{3}{8}$ Vậy A=$\frac{3}{8}$ Bình luận
A=$\frac{1}{6}$ + $\frac{1}{12}$ + $\frac{1}{20}$ +$\frac{1}{30}$ +$\frac{1}{42}$ +$\frac{1}{56}$
=$\frac{1}{2.3}$ + $\frac{1}{3.4}$ + $\frac{1}{4.5}$ +$\frac{1}{5.6}$ +$\frac{1}{6.7}$ +$\frac{1}{7.8}$
=$\frac{3-2}{2.3}$ + $\frac{4-3}{3.4}$ + $\frac{5-4}{4.5}$ +$\frac{6-5}{5.6}$ +$\frac{7-6}{6.7}$ +$\frac{8-7}{7.8}$
=$\frac{1}{2}$ – $\frac{1}{3}$ + $\frac{1}{3}$- $\frac{1}{4}$+$\frac{1}{4}$ -$\frac{1}{5}$ +$\frac{1}{5}$-$\frac{1}{6}$ +$\frac{1}{6}$-$\frac{1}{7}$+$\frac{1}{7}$-$\frac{1}{8}$
=$\frac{1}{2}$ -$\frac{1}{8}$
=$\frac{3}{8}$
Vậy A=$\frac{3}{8}$
A=1/6+1/12+1/20+1/30+1/42+1/56
=1/4+2/15+1/24
=23/60+1/24
=17/40