\(=\dfrac{2x4x3x6x5x5}{2x4x3x5x3x6}=\dfrac{5}{3}\)?

\(\dfrac{2\times4\times18\times25}{24\times5\times3\times6}=\dfrac{2\times4\times6\times3\times5\times5}{2\times3\times4\times5\times3\times6}=\dfrac{5}{3}\)  

\(\dfrac{6}{13}.\dfrac{5}{7}+\dfrac{6}{13}.\dfrac{2}{7}+\dfrac{7}{13}=\dfrac{6}{13}.\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\dfrac{7}{13}=\dfrac{6}{13}.1+\dfrac{7}{13}=\dfrac{6}{13}+\dfrac{7}{13}=\dfrac{13}{13}=1\)

#Monster

\(\dfrac{6}{13}\).(\(\dfrac{2}{7}+\dfrac{5}{7}\))+\(\dfrac{7}{13}\)

\(\dfrac{6}{13}\).1+\(\dfrac{7}{13}\)

\(\dfrac{6}{13}\)+\(\dfrac{7}{13}\)

1

mik làm ở bài dưới rồi nha.

4/9 x 11 + 4/11 x 13 + 4/13 x 15 + ... + 4/97 x 99

= 2(1/9 - 1/11 + 1/11 - 1/13 + ... + 1/97 - 1/99)

= 2(1/9 - 1/99)

= 20/99

Chúc bạn học tốt!

Bằng 20/99 nhé

\(1\dfrac{4}{5}+2\dfrac{5}{7}+3\dfrac{4}{5}+4\dfrac{5}{7}\)

\(\text{=}\left(1\dfrac{4}{5}+3\dfrac{4}{5}\right)+\left(2\dfrac{5}{7}+4\dfrac{5}{7}\right)\)

\(\text{=}1+3+\left(\dfrac{4}{5}+\dfrac{4}{5}\right)+2+4+\left(\dfrac{5}{7}+\dfrac{5}{7}\right)\)

\(\text{=}10+\dfrac{8}{5}+\dfrac{10}{7}\text{=}131\dfrac{1}{35}\)

= \(\dfrac{11}{15}\). \(\left(\dfrac{4}{11}+\dfrac{5}{11}+\dfrac{2}{11}\right)\)

= \(\dfrac{11}{15}\). 1

=\(\dfrac{11}{15}\)

\(=\dfrac{11}{15}\cdot\left(\dfrac{4}{11}+\dfrac{5}{11}+\dfrac{2}{11}\right)=\dfrac{11}{15}\cdot\dfrac{11}{11}=\dfrac{11}{15}\)

11/15 . ( 4/11 +5/11 + 2/11 )

= 11/15 . 1

= 11/15

\(\dfrac{1}{19}+\dfrac{9}{19\cdot29}+...+\dfrac{9}{1999\cdot2009}\)

\(=\dfrac{1}{19}+\dfrac{9}{10}\left(\dfrac{10}{19\cdot29}+...+\dfrac{10}{1999\cdot2009}\right)\)

\(=\dfrac{1}{19}+\dfrac{9}{10}\left(\dfrac{1}{19}-\dfrac{1}{2009}\right)\)

\(=\dfrac{1}{19}+\dfrac{1791}{38171}=\dfrac{200}{2009}\)

=1 phần 3*4+1 phần 4*5+1 phần 5*6+...+1 phần 98*99

=1 phần 3-1 phần 4+ 1 phần 4- 1 phần 5+...+1 phần 98-1 phần 99

=1 phần 3- 1 phần 99                      =32 phần 99

\(\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+...+\dfrac{1}{9702}=\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+...+\dfrac{1}{98\cdot99}=\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+...+\dfrac{1}{98}-\dfrac{1}{99}=\dfrac{1}{3}-\dfrac{1}{99}=\dfrac{33-1}{99}=\dfrac{32}{99}\)

\(\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+...+\dfrac{1}{9702}\)

= \(\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+...+\dfrac{1}{98.99}\)

= \(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+...+\dfrac{1}{98}-\dfrac{1}{99}\)

= \(\dfrac{1}{3}-\dfrac{1}{99}\)

= \(\dfrac{33}{99}-\dfrac{1}{99}\)

= \(\dfrac{32}{99}\)

..... làm j thế

( \(\dfrac{13}{17}\) + \(\dfrac{4}{17}\) ) + (\(\dfrac{2}{13}\) + \(\dfrac{11}{13}\) ) = \(\dfrac{17}{17}\) + \(\dfrac{13}{13}\) = \(1\) + \(1\) = \(2\).

76/34+98/100+38/17+49/50

= 76/34+98/100+76/34+98/100

=( 76/34+76/34)+ (98/100+98/100)

=152/34+196/100

= 2733/425

ht