Bài làm :

\(\dfrac{5}{13}+\dfrac{5}{17}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{5}{17}\)

\(=1+\left(-1\right)+\dfrac{5}{17}\)

\(=0+\dfrac{5}{17}=\dfrac{5}{7}\)

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\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{5}{17}\)

\(=1+\left(-1\right)+\dfrac{5}{17}\)

\(=0+\dfrac{5}{17}\)

\(=\dfrac{5}{17}\)

\(\dfrac{5}{13}+\dfrac{5}{17}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

= \(\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{5}{17}\)

= \(1+\left(-1\right)+\dfrac{5}{17}\)

= \(0+\dfrac{5}{17}\)

= \(\dfrac{5}{17}\)

= -103/273

= 0

= -5/7

5.\(-\dfrac{3}{7}+\dfrac{5}{13}+\dfrac{-4}{12}=-\dfrac{103}{273}\)

b.\(-\dfrac{5}{21}+\dfrac{-2}{21}+\dfrac{8}{24}=\dfrac{-5-2}{21}+\dfrac{8}{24}=-\dfrac{7}{21}+\dfrac{8}{24}=-\dfrac{1}{3}+\dfrac{8}{24}=0\)

c.\(\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+-\dfrac{5}{7}=1-1-\dfrac{5}{7}=-\dfrac{5}{7}\)

1: =5/13+8/13-20/41-21/41-5/17

=1-1-5/17=-5/17

2: =1/5+4/5-2/9-7/9+16/17

=16/17+1-1=16/17

3: =1/3-1/5+1/5-1/7+...+1/99-1/101

=1/3-1/101

=98/303

Ta có: \(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)

\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)

\(=1-1+\dfrac{-5}{7}\)

\(=\dfrac{-5}{7}\)

Có 2 dấu = hả bạn

\(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}=(\dfrac{5}{13}+\dfrac{8}{13})+(\dfrac{-20}{41}+\dfrac{-21}{41})+(\dfrac{-5}{7})=1+\left(-1\right)+\dfrac{-5}{7}=0+\dfrac{-5}{7}=\dfrac{-5}{7}\)

a/ \(\dfrac{11}{24}-\dfrac{5}{41}+\dfrac{13}{24}+0,5-\dfrac{36}{41}\)

\(=\left(\dfrac{11}{24}+\dfrac{13}{24}\right)+\left(-\dfrac{5}{41}-\dfrac{36}{41}\right)+0,5\)

\(=1+\left(-1\right)+0,5\)

\(=0+0,5=0,5\)

b/ \(23\dfrac{1}{4}.\dfrac{7}{5}-13\dfrac{1}{4}:\dfrac{5}{7}\)

\(=23\dfrac{1}{4}.\dfrac{7}{5}-13\dfrac{1}{4}.\dfrac{7}{5}\)

\(=\dfrac{7}{5}\left(23\dfrac{1}{4}-13\dfrac{1}{4}\right)\)

\(=\dfrac{7}{5}.10\)

\(=14\)

a 0.5

b 14

0.5

14

`(x-3/8) +1/4= 7/8`

`=> x-3/8 = 7/8-1/4`

`=> x-3/8 = 7/8-2/8`

`=> x-3/8 =5/8`

`=>x= 5/8 +3/8`

`=>x= 8/8=1`

3)\(\dfrac{-41}{32}\left(\dfrac{15}{8}-\dfrac{16}{41}\right)+\dfrac{15}{8}\left(\dfrac{41}{32}-\dfrac{8}{3}\right)\)

=\(\dfrac{-41}{32}.\dfrac{15}{8}-\dfrac{-41}{32}.\dfrac{16}{41}+\dfrac{15}{8}.\dfrac{41}{32}-\dfrac{15}{8}.\dfrac{8}{3}\)

=\(\left(\dfrac{-41}{32}.\dfrac{15}{8}+\dfrac{15}{8}.\dfrac{41}{32}\right)+\dfrac{-16}{41}.\dfrac{-41}{32}-\dfrac{15}{8}.\dfrac{8}{3}\)

=\(0+\dfrac{1}{2}-5=\dfrac{-9}{2}\)

4)\(\dfrac{13}{29}\left(\dfrac{29}{5}-\dfrac{45}{8}\right)-\dfrac{45}{8}\left(\dfrac{9}{8}-\dfrac{13}{29}\right)\)

=\(\dfrac{13}{29}.\dfrac{29}{5}-\dfrac{45}{8}.\dfrac{13}{29}-\dfrac{45}{8}.\dfrac{9}{8}-\dfrac{45}{8}.\dfrac{13}{29}\)

=\(\left(\dfrac{45}{8}.\dfrac{13}{29}-\dfrac{45}{8}.\dfrac{13}{29}\right)-\dfrac{13}{29}.\dfrac{29}{5}-\dfrac{45}{8}.\dfrac{9}{8}\)

=\(0-\dfrac{13}{5}-\dfrac{405}{64}=\dfrac{-2857}{320}\)

a. $8\frac{5}{7}+3,15+1\frac{2}{7}+4,35$

$\mathrm{=\backslash (\backslash dfrac\{61\}\{7\}+\backslash dfrac\{63\}\{20\}+\backslash dfrac\{9\}\{7\}+\backslash dfrac\{87\}\{20\}\backslash )}$

=\(\left(\dfrac{61}{7}+\dfrac{9}{7}\right)+\left(\dfrac{63}{20}+\dfrac{87}{20}\right)\)

=\(10+\dfrac{15}{2}\)

=\(\dfrac{35}{2}\)

b. $\left(4\frac{5}{23}-2\frac{2}{5}+7\frac{7}{13}\right)-\left(3\frac{5}{23}-6\frac{6}{13}\right)$

$=\backslash (4\backslash dfrac\{5\}\{23\}-2\backslash dfrac\{2\}\{5\}+7\backslash dfrac\{7\}\{13\}-3\backslash dfrac\{5\}\{23\}+6\backslash dfrac\{6\}\{13\}\backslash )$

=\(\left(4\dfrac{5}{23}-3\dfrac{5}{23}\right)+\left(7\dfrac{7}{13}+6\dfrac{6}{13}\right)-2\dfrac{2}{5}\)

=\(1+14-\dfrac{12}{5}\)

=15-\(\dfrac{12}{5}\)

=\(\dfrac{63}{5}\)

Câu C khó khó mình chưa giải được !!!