tính nhanh
20/41+13/21+21/41+8/21=
phân số được viết dưới dạng a/b
K
Khách
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H9
HT.Phong (9A5)
CTVHS
27 tháng 7 2023
\(\dfrac{5}{13}+\dfrac{-5}{17}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)
\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\dfrac{-5}{17}+\left(\dfrac{-20}{41}-\dfrac{21}{41}\right)\)
\(=\dfrac{13}{13}+\dfrac{-5}{17}+\dfrac{-41}{41}\)
\(=1-\dfrac{5}{17}-1\)
\(=-\dfrac{5}{17}\)
23 tháng 3 2021
Ta có: \(A=\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}\)
\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+\dfrac{-5}{7}\)
\(=1-1+\dfrac{-5}{7}\)
\(=\dfrac{-5}{7}\)
M
4
21 tháng 2 2018
-207/221
đây chỉ là kết quả thôi cách làm mình sẽ đăng sau
Y
16 tháng 2 2023
\(\dfrac{5}{13}+\left(-\dfrac{5}{7}\right)+\left(-\dfrac{20}{41}\right)+\dfrac{8}{13}+\left(-\dfrac{21}{41}\right)\)
\(=\dfrac{5}{13}-\dfrac{5}{7}-\dfrac{20}{41}+\dfrac{8}{13}-\dfrac{21}{41}\)
\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)-\left(\dfrac{20}{41}+\dfrac{21}{41}\right)-\dfrac{5}{7}\)
\(=\dfrac{13}{13}-\dfrac{41}{41}-\dfrac{5}{7}\)
\(=1-1-\dfrac{5}{7}\)
\(=0+\dfrac{5}{7}\)
\(=\dfrac{5}{7}\)
16 tháng 4 2022
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.\(\dfrac{5}{13}+\dfrac{-5}{7}+\dfrac{-20}{41}+\dfrac{8}{13}+\dfrac{-21}{41}=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\left(\dfrac{-20}{41}+\dfrac{-21}{41}\right)+-\dfrac{5}{7}=1-1-\dfrac{5}{7}=-\dfrac{5}{7}\)
LT
2
NK
25 tháng 2 2023
\(a,\dfrac{2}{5}-\dfrac{3}{8}+\dfrac{7}{6}=\dfrac{16}{40}-\dfrac{15}{40}+\dfrac{7}{6}=\dfrac{1}{40}+\dfrac{7}{6}=\dfrac{3}{120}+\dfrac{140}{120}=\dfrac{143}{120}\)
\(b,\dfrac{2}{3}+\left[\dfrac{5}{7}+\left(-\dfrac{2}{3}\right)\right]=\dfrac{2}{3}+\dfrac{5}{7}+\left(-\dfrac{2}{3}\right)=\left[\dfrac{2}{3}+\left(-\dfrac{2}{3}\right)\right]+\dfrac{5}{7}=0+\dfrac{5}{7}=\dfrac{5}{7}\)
\(c,\dfrac{5}{13}+\left(-\dfrac{5}{7}\right)+\left(-\dfrac{20}{41}\right)+\dfrac{8}{13}+\left(-\dfrac{21}{41}\right)\)
\(=\left(\dfrac{5}{13}+\dfrac{8}{13}\right)-\dfrac{5}{7}-\dfrac{20}{41}-\dfrac{21}{41}=-\dfrac{5}{7}\)
25 tháng 2 2023
a: =48/120-45/120+140/120
=143/120
b: =2/3-2/3+5/7=5/7
c: =5/13+8/13-5/7-20/41-21/41
=-5/7
\(\dfrac{20}{41}+\dfrac{13}{21}+\dfrac{21}{41}+\dfrac{8}{21}\)
\(=\left(\dfrac{20}{41}+\dfrac{21}{41}\right)+\left(\dfrac{13}{21}+\dfrac{8}{21}\right)\)
\(=\dfrac{41}{41}+\dfrac{21}{21}\)
\(=\dfrac{1}{1}+\dfrac{1}{1}\)
\(=1+1\)
\(=2\)