\(\frac{5}{6}+\frac{5}{12}+\frac{5}{20}+\frac{5}{30}+...+\frac{5}{132}+\)\(\frac{5}{156}\)
\(=5\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{132}+\frac{1}{156}\right)\)
\(=5\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{11.12}+\frac{1}{12.13}\right)\)
\(=5\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{11}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}\right)\)
\(=5\left(\frac{1}{2}-\frac{1}{6}\right)\)
\(=5.\frac{1}{3}\)
\(=\frac{5}{3}\)
( Dấu \(.\)là dấu \(\times\)nha )
5/6+5/12+5/20+...+5/132+5/156
=5*(1/6+1/12+1/20+...+1/132+1/156)
=5*[1/(2*3)+1/(3*4)+...+1/(11*12)+1/(12*13)]
=5*(1/2-1/3+1/3-1/4+..+1/11-1/12+1/12-1/13)
=5*(1/2-1/13)
=5*(11/26)
=55/26
\(\frac{5}{6}+\frac{5}{12}+\frac{5}{20}+\frac{5}{30}+...+\frac{5}{132}+\frac{5}{156}\)
\(=\frac{5}{2.3}+\frac{5}{3.4}+\frac{5}{4.5}+\frac{5}{5.6}+...+\frac{5}{11.12}+\frac{5}{12.13}\)
\(=5.\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{11.12}+\frac{1}{12.13}\right)\)
\(=5.\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{11}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}\right)\)
\(=5.\left(\frac{1}{2}-\frac{1}{13}\right)\)
\(=5.\frac{11}{26}=\frac{55}{26}\)
Khổng Mai Linh làm đúng nhưng đến bước 5 lại nhầm
Cho mk sửa lại ( xin lỗi nha )
\(=5\left(\frac{1}{2}-\frac{1}{13}\right)\)
\(=5.\frac{11}{26}\)
\(=\frac{55}{26}\)
XIN LỖI NHA
\(\frac{5}{6}+\frac{5}{12}+\frac{5}{20}+\frac{5}{30}+...+\frac{5}{132}+\frac{5}{156}\)
\(=\frac{5}{2x3}+\frac{5}{3x4}+\frac{5}{4x5}+\frac{5}{5x6}+...+\frac{5}{11x12}+\frac{5}{12x13}\)
\(=5x\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{11}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}\right)\)
\(=5x\left(\frac{1}{2}-\frac{1}{13}\right)\)
\(=5x\frac{11}{26}\)
\(=\frac{55}{26}\)
