Question

Tìm giá trị của biểu thức: \(M=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4+5}=\)

Answer 1

\(\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4+5}\)  = \(\frac{1}{3}+\frac{1}{6}+\frac{1}{15}\)= \(\frac{10}{30}+\frac{5}{30}+\frac{2}{30}\)= \(\frac{10+5+2}{30}\)= \(\frac{17}{30}\)

Answer 2

Trong đề có 4 đáp án là a)\(\frac{1}{6}\)

b)\(\frac{5}{6}\)

c) \(\frac{1}{3}\)

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

Answer 3

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

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

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

= \(\frac{10+5+2}{30}\)

= \(\frac{17}{30}\)

Vậy M = \(\frac{17}{30}\)

Answer 4

ak thiếu 1 cái là \(\frac{1}{1+2+3+4}\)

Answer 5

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

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

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

= \(\frac{10+5+3+2}{30}\)

= \(\frac{20}{30}\)

= \(\frac{2}{3}\)

Lần sau phải ghi đề đúng đừng ghi thiếu nhé

Answer 6

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

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

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

\(=\frac{10+5+3+2}{30}=\frac{20}{30}=\frac{2}{3}\)