12 x 9 + 9,7

= 108 + 9,7

= 117,7

chúc bạn hok tốt ^-^

117,7 nha !

   12 x 9 +9,7

= 108 +9,7

= 117,7

    m = 1/3-1/5+1/5-1/7+1/7-1/9+...+1/97-1/99

    m = 1/3-1/99=32/99

   Sorry chị em ko làm đc câu b vì em mới học lớp 4

   k em ha

a) \(M=\frac{2}{3\times5}+\frac{2}{5\times7}+\frac{2}{7\times9}+...+\frac{2}{97\times99}\)

\(\Rightarrow M=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{97}-\frac{1}{99}\)

\(\Rightarrow M=\frac{1}{3}-\frac{1}{99}\)

\(\Rightarrow M=\frac{33}{99}-\frac{1}{99}=\frac{32}{99}\)

b)  \(N=\frac{3}{5\times7}+\frac{3}{7\times9}+\frac{3}{9\times11}+...+\frac{3}{197\times199}\)

\(\Rightarrow N=3\times\left(\frac{1}{5\times7}+\frac{1}{7\times9}+\frac{1}{9\times11}+...+\frac{1}{197\times199}\right)\)

\(\Rightarrow N=3\times\left[2\times\left(\frac{1}{5\times7}+\frac{1}{7\times9}+\frac{1}{9\times11}+...+\frac{1}{197\times199}\right)\right]\)

\(\Rightarrow N=3\times\left(\frac{2}{5\times7}+\frac{2}{7\times9}+\frac{2}{9\times11}+...+\frac{2}{197\times199}\right)\)

\(\Rightarrow N=3\times\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{197}-\frac{1}{199}\right)\)

\(\Rightarrow N=3\times\left(\frac{1}{5}-\frac{1}{199}\right)\)

\(\Rightarrow N=3\times\frac{194}{995}=\frac{582}{995}\)

----Chúc em học giỏi !----

a M=1/3-1/5+1/5-1/7+1/7-1/9+....+1/97-1/99

M=1/3-1/99

M= 33/99-1/99

M=32/99

b

N=3/2( 2/5x7+2/7x9+2/9x11+...+ 2/ 197x199)

N=3/2x(1/5-1/7+1/7-1/9+1/9-1/11+.....+ 1/197-1/199)

N=3/2x( 1/5-1/199)

N=3/2x194/995

N=291/995

chắc chắn đúng 100% nha bạn

x+702=405  x=-297                                                                                       

\(x+78\cdot9=9\cdot45\)

\(\Leftrightarrow x+702=405\)

\(\Leftrightarrow x=-297\)

x + 78 x 9 = 9 x 45

x + 78 x 9 = 405

x + 702 = 405

x = 405 - 702

x= -297

\(12\frac{3}{7}\%+12\frac{5}{7}\%=\frac{176}{7}\%\)

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  = \(\frac{-11}{14}\)

=30/4

ko hề khó

7 + 2/4

= 28/4 + 2/4

= 30/4

= 15/2

=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

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

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

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

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

\(12\frac{4}{5}\)=\(\frac{64}{5}\).

Ta có :

\(\frac{64}{5}+\frac{4}{5}=\frac{68}{5}\)

\(12\frac{4}{5}+\frac{4}{5}=\frac{64}{5}+\frac{4}{5}=\frac{68}{5}\)

\(12\frac{4}{5}+\frac{4}{5}=\frac{12x5+4}{5}+\frac{4}{5}=\frac{64}{5}+\frac{4}{5}=\frac{68}{5}\)