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26 tháng 10 2021
Bài 4:
\(\Leftrightarrow n+1\in\left\{1;3\right\}\)
hay \(n\in\left\{0;2\right\}\)
26 tháng 10 2021
\(\left(n+4\right)⋮\left(n+1\right)\Rightarrow\left(n+1\right)+3⋮\left(n+1\right)\)
\(\Rightarrow\left(n+1\right)\inƯ\left(3\right)=\left\{-3;-1;1;3\right\}\)
Mà \(n\in N\)
\(\Rightarrow n\in\left\{0;2\right\}\)
21 tháng 2 2020
72x(28-49)+28x(-49-72)
=72x(-21)+28x(-121)
=-1512+(-3388)
=-49900
21 tháng 2 2020
Có 2 cách hiểu
+ ) 72x( 28 - 49 ) + 28x( -49 - 72)
= 72x . 28 - 72x . 49 - 28x . 49 - 28x . 72
= -72x . 49 - 28x . 49
= 49 . ( - 100x )
+) 72 . ( 28 - 49 ) + 28 . ( -49 - 72 )
= 72 . 28 - 72 . 49 -28 . 49 - 28 . 72
= -72 . 49 -28 . 49
= 49 . ( -100 ) = -4900
VN
1
NA
27 tháng 11 2021
c) (519 - 17 + 3) : 7
= (52 + 3) : 7
= (25 + 3) : 7
= 28 : 7
= 4
Y
25 tháng 4 2022
\(49,=\dfrac{38}{5}-\left(\dfrac{19}{7}+\dfrac{28}{5}\right)\)
\(=\dfrac{38}{5}-\dfrac{19}{7}-\dfrac{28}{5}\)
\(=\left(\dfrac{38}{5}-\dfrac{28}{5}\right)-\dfrac{19}{7}\)
\(=2-\dfrac{19}{7}=-\dfrac{5}{7}\)
\(50,=\dfrac{25}{81}.\dfrac{15}{22}=\dfrac{125}{594}\)
25 tháng 4 2022
mik xinloi ạ câu 50 mik viết sai đề nên mong bạn giải lại giúp ạ <3
19 tháng 4 2021
(1-1/2)×(1-1/3)×(1-1/4)×....×(1-1/100)
=(2/2-1/2)x(3/3-1/3)x...x(100/100-1/100)
=1/2x2/3x...x99/100
=1/100
6 tháng 1 2022
Câu 2:
1: \(\Leftrightarrow x\cdot\dfrac{7}{2}=\dfrac{9}{2}+3=\dfrac{15}{2}\)
hay x=15/7
2: \(\Leftrightarrow x=\dfrac{5}{2}\cdot\dfrac{8}{5}=4\)
3: \(\Leftrightarrow x=\dfrac{-11\cdot10}{5}=-11\cdot2=-22\)
4: =>2x=90
hay x=45
15 tháng 4 2021
22. \(\dfrac{\dfrac{3}{4}+\dfrac{3}{7}-\dfrac{3}{8}}{\dfrac{5}{4}+\dfrac{5}{7}-\dfrac{5}{8}}+1=\dfrac{3\left(\dfrac{1}{4}+\dfrac{1}{7}-\dfrac{1}{8}\right)}{5\left(\dfrac{1}{4}+\dfrac{1}{7}-\dfrac{1}{8}\right)}+1=\dfrac{3}{5}+1=\dfrac{8}{5}\)
23. \(\dfrac{2}{5}+\dfrac{3}{5}:\left(\dfrac{3}{5}+\dfrac{-2}{3}\right)+\dfrac{7}{2}=\dfrac{2}{5}+\dfrac{3}{5}:\left(\dfrac{9-10}{15}\right)+\dfrac{7}{2}=\dfrac{2}{5}+\dfrac{3}{5}.\dfrac{-15}{1}+\dfrac{7}{2}=\dfrac{2}{5}-\dfrac{45}{5}+\dfrac{7}{2}\)
\(=\dfrac{4}{10}-\dfrac{90}{10}+\dfrac{35}{10}=\dfrac{4-90+35}{10}=-\dfrac{51}{10}\)
24. \(\dfrac{4+\dfrac{4}{73}-\dfrac{4}{115}}{5+\dfrac{5}{73}-\dfrac{1}{23}}=\dfrac{4\left(1+\dfrac{1}{73}-\dfrac{1}{115}\right)}{5+\dfrac{5}{73}-\dfrac{5}{115}}=\dfrac{4\left(1+\dfrac{1}{73}-\dfrac{1}{115}\right)}{5\left(1+\dfrac{1}{73}-\dfrac{1}{115}\right)}=\dfrac{4}{5}\)
15 tháng 4 2021
4. \(\dfrac{5}{7}-\dfrac{2}{11}+\dfrac{5}{7}-\dfrac{9}{11}=\dfrac{5}{7}\left(-\dfrac{2}{11}-\dfrac{9}{11}\right)=-\dfrac{5}{7}\)
9. \(\dfrac{5}{9}.\dfrac{7}{13}+\dfrac{5}{9}.\dfrac{9}{13}-\dfrac{5}{9}.\dfrac{3}{13}=\dfrac{5}{9}\left(\dfrac{7}{13}+\dfrac{9}{13}-\dfrac{3}{13}\right)=\dfrac{5}{9}\)
10. \(\dfrac{-5}{9}+\dfrac{8}{15}-\dfrac{2}{11}-\dfrac{4}{9}+\dfrac{7}{15}=\left(-\dfrac{5}{9}-\dfrac{4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)-\dfrac{2}{11}=-\dfrac{2}{11}\)
Bài 4:
\(a,\Rightarrow5⋮x\Rightarrow x\inƯ\left(5\right)=\left\{1;5\right\}\\ b,\Rightarrow x-2+7⋮x-2\\ \Rightarrow x-2\inƯ\left(7\right)=\left\{1;7\right\}\\ \Rightarrow x\in\left\{3;9\right\}\\ c,\Rightarrow3\left(x+1\right)+4⋮x+1\\ \Rightarrow x+1\inƯ\left(4\right)=\left\{1;2;4\right\}\\ \Rightarrow x\in\left\{0;1;3\right\}\\ d,\Rightarrow10x+6⋮2x-1\\ \Rightarrow5\left(2x-1\right)+11⋮2x-1\\ \Rightarrow2x-1\inƯ\left(11\right)=\left\{1;11\right\}\\ \Rightarrow x\in\left\{1;6\right\}\\ e,\Rightarrow x\left(x+3\right)+11⋮x+3\\ \Rightarrow x+3\inƯ\left(11\right)=\left\{1;11\right\}\\ \Rightarrow x=8\left(x\in N\right)\\ f,\Rightarrow x\left(x+3\right)+2\left(x+3\right)+5⋮x+3\\ \Rightarrow x+3\inƯ\left(5\right)=\left\{1;5\right\}\\ \Rightarrow x=2\left(x\in N\right)\)