21/10 - 3/4 - 2/5=
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19 tháng 4 2017
A . \(3\cdot\dfrac{5}{4}-\dfrac{3^2}{4}=\dfrac{15}{4}-\dfrac{9}{4}=\dfrac{6}{4}=\dfrac{3}{2}\)
B, \(\dfrac{-3}{2}\cdot\left(\dfrac{7}{3}-\dfrac{5}{3}\cdot4\right)=\dfrac{-3}{2}\cdot\left(\dfrac{7}{3}-\dfrac{20}{3}\right)=\dfrac{-3}{2}\cdot\dfrac{-13}{2}=\dfrac{39}{4}\)
C , \(\dfrac{-21}{10}+\dfrac{21}{10}\cdot\dfrac{3}{4}-\dfrac{3}{4}=\dfrac{-84}{40}+\dfrac{63}{40}-\dfrac{30}{40}=\dfrac{-84+63-30}{40}=\dfrac{-51}{40}\)
D , \(\dfrac{-2}{3}+2\cdot\left(\dfrac{-2}{3}\right)\cdot3-3=\dfrac{-2}{3}\left(1+2\cdot3\right)-3=\dfrac{-2}{3}\cdot7-3=\dfrac{-14}{3}-\dfrac{9}{3}=-\dfrac{23}{3}\)
LM
Lê Minh Vũ
VIP
15 tháng 6 2023
3 x 15 + 21 x 15 + 85 x 5
= 45 + 315 + 425
= 785
15 - 30 + 40
= 25
21 + 19 - 50 + 10
= 0
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=-\dfrac{1}{20}+2\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{12}\times\dfrac{3}{12}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=-\dfrac{9}{20}\)
BD
15 tháng 6 2023
\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)
\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)
\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)
\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)
\(=\dfrac{44}{20}-\dfrac{5}{20}\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)
\(=\dfrac{6}{20}-\dfrac{15}{20}\)
\(=-\dfrac{9}{20}\)
24 tháng 1 2022
a, 5/-14. 7/-19=8/38
b, -15/4 .( 16/-25 )=12/5
c, 3/-10 .( -15/-2 )=
d, -5/7 . ( 21/-10 )=-9/4
e, 10/-3. (6/-5)==4
f, 21/-9 . ( -6/14 )=1
g, -10/9 . ( 36/20 )=-2
12 tháng 11 2021
c: \(=\dfrac{3}{2}\cdot1-1-20=\dfrac{3}{2}-21=\dfrac{-39}{2}\)
PT
1
19 tháng 9 2018
\(\frac{27^3+9^{10}.2^4+4^2.81^5}{3^{10}+3^{21}.2^5}\)
=\(\frac{3^9+3^{20}.2^4+2^4.3^{20}}{3^{10}+3^{21}.2^5}\)
=\(\frac{3^{18}+2^3}{1}\)
= \(3^{18}+2^3\)
Hk tốt
20 tháng 1
a: \(C=\dfrac{-1}{2}:\dfrac{-2}{3}:\dfrac{-3}{4}\)
\(=\dfrac{-1}{2}\cdot\dfrac{3}{-2}\cdot\dfrac{4}{-3}\)
\(=-\dfrac{4}{4}=-1\)
b: \(D=\dfrac{-6}{5}:\dfrac{-5}{4}:\dfrac{-4}{3}\)
\(=-\dfrac{6}{5}\cdot\dfrac{4}{5}\cdot\dfrac{3}{4}\)
\(=\dfrac{-18}{25}\)
c: \(\dfrac{4}{20}+\dfrac{16}{42}+\dfrac{6}{15}+\dfrac{-3}{5}+\dfrac{2}{21}+\dfrac{-10}{21}+\dfrac{3}{20}\)
\(=\left(\dfrac{4}{20}+\dfrac{-3}{5}+\dfrac{6}{15}\right)+\left(\dfrac{16}{42}+\dfrac{2}{21}-\dfrac{10}{21}\right)+\dfrac{3}{20}\)
\(=\left(\dfrac{1}{5}-\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{8}{21}+\dfrac{2}{21}-\dfrac{10}{21}\right)+\dfrac{3}{20}\)
\(=\dfrac{3}{20}\)
d: \(\dfrac{42}{46}+\dfrac{250}{186}+\dfrac{-2121}{2323}+\dfrac{-125125}{143143}\)
\(=\dfrac{21}{23}+\dfrac{125}{93}+\dfrac{-21}{21}+\dfrac{-125}{143}\)
\(=\dfrac{125}{93}-\dfrac{125}{143}=\dfrac{6250}{13299}\)
12 tháng 11 2021
c: \(=\dfrac{3}{2}-1-21=\dfrac{3}{2}-21=\dfrac{-39}{2}\)
\(\dfrac{21}{10}-\dfrac{3}{4}-\dfrac{2}{5}=\dfrac{42}{20}-\dfrac{15}{20}-\dfrac{8}{20}\)
\(=\dfrac{42-15-8}{20}\)
\(=\dfrac{19}{20}\)
mẫu số chung là 20 nên
21/10x2=42/20
3/4x2=15/20
2/5x2=8/20
lấy 42/20-15/20-8/20=19/20 nha