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 !!!

 12 x 6 + 12 x 3 + 12

= 12 x ( 6 + 3 + 1 )

= 12 x   10

=   120

 12 x (6+3+1)

=12 X 10

=120

12x6+12x3+12

=12x(6+3+1)

=12x10

=120

\(89+\frac{2}{12}=89+\frac{1}{6}=\frac{534}{6}+\frac{1}{6}=\frac{534+1}{6}=\frac{535}{6}\)

AI THẤY ĐÚNG NHỚ ỦNG HỘ NHA

\(89+\frac{2}{12}=\frac{535}{6}\)

Tk cho mình nha vì mình đang bị âm điểm

\(89+\frac{2}{12}\)

\(=89+\frac{1}{6}\)

\(=\frac{535}{6}\)

Vậy 89 + 2/12 = 535/6

mình nè

= 2x4/3x4 + 3x3/4x3 +3/12=8/12+9/12+3/12=8+9+3/12=20/12=5/3

dễ sợ thiệt

Mấy bạn dùng mấy cái này để xin đúng

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  = \(\frac{-11}{14}\)

\(12\frac{4}{3}+\frac{2}{6}=\frac{41}{3}\)

\(12\frac{4}{3}+\frac{2}{6}=16+\frac{1}{3}=\frac{49}{3}\)

12 + 4/3 + 2/6 = 12 + 5/3 = 41/3

\(9\frac{5}{34}-12+5\)

\(9\frac{5}{34}=\frac{311}{34}\)

\(\Rightarrow9\frac{5}{34}-12+5\)

\(=\frac{311}{34}-12+5\)

\(=-\frac{97}{34}+5\)

\(=\frac{73}{34}\)

= \(\frac{69}{34}\)

Mk kb rùi đó , tk mk nha !

\(9\frac{5}{34}-12+5\)

\(=\frac{311}{34}-12+5\)

\(=-\frac{97}{34}+5\)

\(=\frac{73}{34}\)

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

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

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

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

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

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

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

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

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

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

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

\(2\frac{4}{3}+\frac{4}{12}=\frac{2.3+4}{3}+\frac{4}{12}=\frac{10}{3}+\frac{4}{12}=\frac{40}{12}+\frac{4}{12}=\frac{44}{12}=\frac{11}{3}\)

\(2\frac{4}{3}=\frac{10}{3}\)

\(\frac{10}{3}+\frac{4}{12}=\frac{120}{36}+\frac{12}{36}\)

\(=\frac{132}{36}=\frac{22}{6}=\frac{11}{3}\)