Question

1\(M=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+\frac{1}{1+2+3+4+5}=\)

Answer 1

kết quả bằng 2/3 

Hok tốt

Answer 2

\(M=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+\frac{1}{1+2+3+4+5}\)

\(M=\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\)

\(M=\frac{2}{3}\)

Answer 3

\(M=\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\)

\(M=\frac{10}{30}+\frac{5}{30}+\frac{3}{30}+\frac{2}{30}\)

\(M=\frac{10+5+3+2}{30}\)

\(M=\frac{20}{30}\)

\(M=\frac{2}{3}\)

HOK TOT

Answer 4

\(M=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}\)\(+\frac{1}{1+2+3+4+5}\)

\(M=\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\)

\(M=\frac{10}{30}+\frac{5}{30}+\frac{3}{30}+\frac{2}{30}\)

\(M=\frac{10+5+3+2}{30}\)

\(M=\frac{20}{30}=\frac{2}{3}\)

Answer 5

M = 1/3+1/6+1/10+1/15

M*1/2=1/3*1/2+1/6*1/2+1/10*1/2+1/15*1/2

M*1/2=1/6+1/12+1/20+1/30

M*1/2=1/2*3+1/3*4+1/4*5+1/5*6

M*1/2=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6

M*1/2=(1/2-1/6)+(1/3-1/3)+(1/4-1/4)+(1/5-1/5)

M*1/2=(3/6-1/6)+0+0+0

M*1/2=2/6

M*1/2=1/3

M=1/3:1/2

M=1/3*2/1

M=2/3

Vậy M = 2/3

Answer 6

\(\frac{1}{1+2}\)\(+\frac{1}{1+2+3}+\)\(\frac{1}{1+2+3+4}+\frac{1}{1+2+3+4+5}\)

=\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+\frac{1}{15}\)

=\(\frac{10}{30}+\frac{5}{30}+\frac{3}{30}+\frac{2}{30}\)

=\(\frac{10+5+3+2}{30}\)

=\(\frac{2}{3}\)