Question

M=54-1/2(1+2)-1/3(1+2+3)-1/4(1+2+3+4)-....-1/12(1+2+....+12)

Answer 1

\(M=54-\frac{1}{2}.\left(1+2\right)-\frac{1}{3}.\left(1+2+3\right)-....-\frac{1}{12}.\left(1+2+...12\right)\)

\(M=54-\left[\frac{1}{2}.\left(1+2\right)+\frac{1}{3}.\left(1+2+3\right)+....+\frac{1}{12}.\left(1+2+...+12\right)\right]\)

\(M=54-\left(\frac{1}{2}\cdot\frac{2.3}{2}+\frac{1}{3}\cdot\frac{3.4}{2}+....+\frac{1}{12}\cdot\frac{12.13}{2}\right)\)

\(M=54-\left(\frac{3}{2}+\frac{4}{2}+...+\frac{13}{2}\right)=54-44=10\)

Vậy M=10

Answer 2

Bài của bạn đúng rồi!Kb nhe!!

Answer 3

Kim Nam Joon BTS bạn là A.R.M.Y à?