Question

\(M=\frac{7}{1\times6}+\frac{7}{16\times11}+\frac{7}{11\times16}+................\frac{7}{256\times261}\)

NÊU CÁCH LÀM GIÙM MÌNH LUÔN NHA

Answer 1

\(M=\frac{7}{1.6}+\frac{7}{6.11}+\frac{7}{11.16}+...+\frac{7}{256.261}\)

\(M=7\left(\frac{1}{1.6}+\frac{1}{6.11}+...+\frac{1}{256.261}\right)\)

\(M=7.\frac{1}{5}\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+...+\frac{1}{256}-\frac{1}{261}\right)\)

\(M=\frac{7}{5}\left(1-\frac{1}{261}\right)\)

\(M=\frac{7}{5}.\frac{260}{261}\)

\(M=\frac{364}{261}\)

Answer 2

nhân 7/5vaof hai vế của M,ta có\(M\frac{5}{ }=\frac{ }{5}.\left(M\right)\\ thành\frac{5}{1.6}+...+\frac{5}{256.261}\\ \)kết quả là52/261