Đặt \(A=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{99.100}\)

\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\)

\(A=1-\frac{1}{100}\)

\(A=\frac{99}{100}\)

cảm ơn bn nhìu ^_^

Ta gọi biểu thức đó là A

Ta có công thức:

\(\frac{a}{b.c}=\frac{a}{c-b}\left(\frac{1}{b}-\frac{1}{c}\right)\)

Dựa vào công thức ta có:

\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\)

\(\Rightarrow\)\(A=1-\frac{1}{100}=\frac{99}{100}\)

Ai thấy đúng thì k nha !!!

=1/2+2+5/3=25/6 tk mk nha mình  là bạn cậu nè

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

k cho mk vs nhé

k cho mk vs nhé

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

= 5/2 x 4/3

=\(\frac{20}{6}\)

M.n tk giùm em vs ạ !! ^_^

\(\frac{25}{2}\%+x=\frac{100}{3}\%\)

                    \(x=\frac{100}{3}\%-\frac{25}{2}\%\)

                    \(x=\frac{200}{6}\%-\frac{75}{6}\%\)

                     \(x=\frac{125}{6}\%\)

= 125 / 6

\(5-1,5-1\frac{1}{2}\)

=\(5-1,5-1,5\)

=\(5-\left(1,5+1,5\right)\)

=\(5-3\)

=\(2\)

= 5 - 1,5 - 1, 5 = 5 - 3 = 2.

Kết bạn cái đầu bà ý :v !!

5- 1, 5 - 1 1/2

= 5 - 1, 5 - 1, 5

= 5 - (1, 5 + 1, 5)

= 5 - 3

= 2

what the hell ?

\(\frac{54}{12}-\frac{5}{3}=\frac{54}{12}-\frac{20}{12}=\frac{34}{12}\)

\(\frac{54}{12}-\frac{5}{3}=\frac{162}{36}-\frac{63}{36}=\frac{102}{36}=\frac{17}{6}\) 

\(\frac{3}{12}+\frac{2}{4}-\frac{2}{12}\)

\(=\frac{3}{12}+\frac{6}{12}-\frac{2}{12}\)

\(=\frac{3+6-2}{12}\)

\(=\frac{7}{12}\)

\(\frac{3}{12}+\frac{2}{4}-\frac{2}{12}\)

\(=\frac{3}{12}+\frac{6}{12}-\frac{2}{12}\)

\(=\frac{9}{12}-\frac{2}{12}\)

\(=\frac{7}{12}\)

\(\frac{3}{12}+\frac{2}{4}-\frac{2}{12}\)

\(=\frac{3}{12}+\frac{6}{12}-\frac{2}{12}\)

\(=\frac{7}{12}\)

2\(\frac{2}{12}\)+ X = \(\frac{5}{7}\)+ \(\frac{8}{12}\)

\(\frac{13}{6}\)+ X=\(\frac{29}{21}\)

X= \(\frac{29}{21}\)- \(\frac{13}{6}\)

X=\(\frac{-11}{14}\)

\(|2^2_{12}\)\(+x=\frac{5}{7}+\frac{8}{12}\)

\(2+x=\frac{5}{7}+\frac{1}{2}\)

\(2+x=\frac{17}{14}\)

\(x=\frac{17}{14}-2\)

\(x=\frac{-11}{14}\)

\(2\frac{2}{12}+x=\frac{5}{7}+\frac{8}{12}\)

\(\frac{26}{12}+x=\frac{29}{21}\)

               x  = \(\frac{29}{21}-\frac{26}{12}\)

              x  = \(\frac{-11}{14}\)