bạn hỏcais gì vậy mình ko hiểu
b= 4/3 + 4/15 + 4/35 + 4/63 + 4/99 + 4/143
là sao vậy bn
kết quả là
7/41
\(B=\frac{4}{3}+\frac{4}{15}+\frac{4}{35}+\frac{4}{63}+\frac{4}{99}+\frac{4}{143}\)
\(B=\frac{4}{1.3}+\frac{4}{3.5}+\frac{4}{5.7}+\frac{4}{7.9}+\frac{4}{9.11}+\frac{4}{11.13}\)
sorry,mình đi ngủ
\(B=\frac{4}{3}+\frac{4}{15}+\frac{4}{35}+\frac{4}{63}+\frac{4}{99}+\frac{1}{143}\)
\(B=\frac{4}{1.3}+\frac{4}{3.5}+\frac{4}{5.7}+\frac{4}{7.9}+\frac{4}{9.11}+\frac{4}{11.13}\)
\(B\div2=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.11}+\frac{2}{11.13}\)
\(B\div2=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}\)
\(B\div2=1-\frac{1}{13}=\frac{12}{13}\)
\(B=\frac{12}{13}.2=\frac{24}{13}\)
