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a) (1/4+3/4)+(-5/13+-8/13)+2/11
=4/4+-13/13+2/11
=1+(-1)+2/11
=2/11
k cho mk nha
\(a,(\frac{1}{4}+\frac{-5}{13})+(\frac{2}{11}+\frac{-8}{13}+\frac{3}{4})\)
\(= (\frac{1}{4} + \frac{3}{4}) + (\frac{-5}{13} + \frac{-8}{13}) + \frac{2}{11}\)
\(= \frac{4}{4} + \frac{-13}{13} + \frac{2}{11}\)
\(=1+(-1)+\frac{2}{11}=\frac{2}{11}\)
\(b,(\frac{21}{31}+\frac{-16}{7})+(\frac{44}{53}+\frac{10}{31})+\frac{9}{53}\)
\(= (\frac{21}{31} + \frac{10}{31}) + (\frac{44}{53} + \frac{9}{53}) + \frac{-16}{7}\)
\(=\frac{31}{31}+\frac{53}{53}+\frac{-16}{7}=1+1-\frac{16}{7}\)
\(=2-\frac{16}{7}=\frac{14}{7}-\frac{16}{7}=-\frac27\)
\(c,\frac{-5}{7}+\frac{3}{4}+\frac{-1}{5}+\frac{-2}{7}+\frac{1}{4}\)
\(= (\frac{-5}{7} + \frac{-2}{7}) + (\frac{3}{4} + \frac{1}{4}) + \frac{-1}{5}\)
\(= \frac{-7}{7} + \frac{4}{4} + \frac{-1}{5}\)
\(=-1+1-\frac{1}{5}=0-\frac15=-\frac15\)
\(\frac{-3}{31} + \frac{-6}{17} + \frac{1}{25} + \frac{-28}{31} + \frac{-11}{17} + \frac{-1}{5}\)
\(= (\frac{-3}{31} + \frac{-28}{31}) + (\frac{-6}{17} + \frac{-11}{17}) + \frac{1}{25} + \frac{-1}{5}\)
\(= \frac{-31}{31} + \frac{-17}{17} + \frac{1}{25} - \frac{5}{25}\)
\(= -1 + (-1) + \frac{-4}{25}\)
\(=-2-\frac{4}{25}=-\frac{50}{25}-\frac{4}{25}=-\frac{54}{25}\)
1/2+2/3+3/4+4/5+5/6+6/7+7/8+8/9+9/10x9/10
=9/10x(1/2+2/3)+(3/4+4/5)+(5/6+6/7)+(7/8+8/9)
=9/10x(1/3+3/5+5/7+7/9)
9/10x(1/3+3/5)+(5/7+7/9)
=9/10x1/5+5/9
9/50+5/9
=10
Bn Long làm đúng rồi bn 
nguyễn kim arica cứ làm theo cách đó là được .
Bn nào thấy đúng thì ủng hộ nha .
Câu a:
(1/4 + -5/13) + (2/11 + -8/13 + 3/4)
= 1/4 - 5/13 + 2/11 - 8/13 + 3/4
= (1/4 + 3/4) - (5/13+ 8/13) + 2/11
= 1 - 1 + 2/11
= 0 + 2/11
= 2/11
Câu b:
(21/31 + -16/7) + (44/53 + 10/31) + 9/53
= 21/31 - 16/7 + 44/53 + 10/31 + 9/53
= (21/31 + 10/31) + (44/53 + 9/53) - 16/7
= 1 + 1 - 16/7
= 2 - 16/7
= -2/7
Câu a:
(1/4 + -5/13) + (2/11 + -8/13 + 3/4)
= 1/4 - 5/13 + 2/11 - 8/13 + 3/4
= (1/4 + 3/4) - (5/13+ 8/13) + 2/11
= 1 - 1 + 2/11
= 0 + 2/11
= 2/11
Câu b:
Câu b:
(21/31 + -16/7) + (44/53 + 10/31) + 9/53
= 21/31 - 16/7 + 44/53 + 10/31 + 9/53
= (21/31 + 10/31) + (44/53 + 9/53) - 16/7
= 1 + 1 - 16/7
= 2 - 16/7
= -2/7
a) \(\left(\frac{1}{4}+-\frac{5}{13}\right)+\left(\frac{2}{11}+-\frac{8}{13}+\frac{3}{4}\right)\)
\(=\frac{2}{11}+\left(\frac{1}{4}+\frac{3}{4}\right)+\left(-\frac{5}{13}+-\frac{8}{13}\right)\)
\(=\frac{2}{11}+1+\left(-1\right)\)
\(=\frac{2}{11}+0\)
\(=\frac{2}{11}\)
b) \(\left(\frac{21}{31}+-\frac{16}{7}\right)+\left(\frac{44}{53}+\frac{10}{31}\right)+\frac{9}{53}\)
\(=-\frac{16}{7}+\left(\frac{21}{31}+\frac{10}{31}\right)+\left(\frac{44}{53}+\frac{9}{53}\right)\)
\(=-\frac{16}{7}+1+1\)
\(=-\frac{16}{7}+2\)
=\(-\frac{2}{7}\)
c) \(\frac{\frac{9}{45}-\frac{4}{13}-\frac{1}{3}}{\frac{3}{13}-\frac{1}{15}+\frac{2}{3}}\)
\(=-\frac{43}{81}\)
b) Áp dụng tính chất
\(\frac{a}{b}< 1\Rightarrow\frac{a}{b}< \frac{a+m}{b+m}\left(m\in N\right)\)
Ta có: \(B=\frac{10^{16}+1}{10^{17}+1}< \frac{10^{16}+1+9}{10^{17}+1+9}=\frac{10^{16}+10}{10^{17}+10}=\frac{10.\left(10^{15}+1\right)}{10.\left(10^{16}+1\right)}=\frac{10^{15}+1}{10^{16}+1}=A\)
\(\Rightarrow B< A\)
\(B< 1\Rightarrow\frac{10^{16}+1}{10^{17}+1}< \frac{10^{16}+1+9}{10^{17}+1+9}=\frac{10^{16}+10}{10^{17}+10}=\frac{10\left(10^{15}+1\right)}{10\left(10^{16}+1\right)}=\frac{10^{15}+1}{10^{16}+1}=A\)
\(\Rightarrow A>B\)