= 1/1.2 + 1/2.3 + 1/3.4 + 1/4.5 + 1/5.6
= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6
= 1 - 1/6
= 5/6
1/2 + 1/6 + 1/12 + 1/20 + 1/30
= 30/60 + 10/60 + 5/60 + 3/60 + 2/60
= 50/60 = 5/6
Có ai đồng tình ý kiến với mình không
[\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}\)] +[ \(\frac{1}{20}+\frac{1}{30}\)]
=\(\frac{9}{12}\)+\(\frac{1}{12}\)
=\(\frac{5}{6}\)