Gọi A=\(\frac{1}{8}+\frac{1}{24}+\frac{1}{48}+\frac{1}{80}+\frac{1}{120}\)
\(A=\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+\frac{1}{8.10}+\frac{1}{10.12}\)
\(2A=\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+\frac{2}{8.10}+\frac{2}{10.12}\)
\(2A=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{10}-\frac{1}{12}\)
\(2A=1-\frac{1}{12}=\frac{11}{12}\)
\(A=\frac{11}{12}:2=\frac{11}{24}\)
bạn ơi ban giúp mình câu này nhé
aa*ab=aab+ab
gọi số cần tìm là A
A= 1\8+1\24+1\48+1\80+1\120
A=1\2x4 +1\4x6 +1\6x8 +1\8x10 +1\10x12
A=1\2-1\4 +1\4 -1\6 +1\6-1\8 +1\8-1\10 +1\10 -1\12
A= 1\2- 1\12
A= 5\12
