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10 tháng 1
Bài 10:
a: \(A=\dfrac{10}{11}+\dfrac{1}{11}\cdot\dfrac{3}{11}+\dfrac{1}{11}\cdot\dfrac{8}{11}\)
\(=\dfrac{10}{11}+\dfrac{1}{11}\left(\dfrac{3}{11}+\dfrac{8}{11}\right)\)
\(=\dfrac{10}{11}+\dfrac{1}{11}=\dfrac{11}{11}=1\)
b: \(B=\dfrac{5}{7}\cdot\dfrac{40}{11}-\dfrac{5}{11}\cdot\dfrac{117}{7}\)
\(=\dfrac{5}{7}\left(\dfrac{40}{11}-\dfrac{117}{11}\right)\)
\(=\dfrac{5}{7}\cdot\dfrac{-77}{11}=\dfrac{5}{7}\cdot\left(-7\right)=-5\)
c: \(C=\dfrac{3}{7}\cdot\dfrac{9}{11}+\dfrac{3}{7}\cdot\dfrac{5}{11}-\dfrac{3}{7}\cdot\dfrac{25}{11}\)
\(=\dfrac{3}{7}\left(\dfrac{9}{11}+\dfrac{5}{11}-\dfrac{25}{11}\right)\)
\(=\dfrac{3}{7}\cdot\dfrac{-11}{11}=-\dfrac{3}{7}\)
d: \(D=\dfrac{5}{7}\cdot\dfrac{-3}{38}\cdot\dfrac{7}{10}\cdot\dfrac{19}{6}\)
\(=\dfrac{5}{7}\cdot\dfrac{7}{10}\cdot\dfrac{-3}{6}\cdot\dfrac{19}{38}\)
\(=\dfrac{5}{10}\cdot\dfrac{-1}{2}\cdot\dfrac{1}{2}=\dfrac{-1}{8}\)
Bài 11:
a: Sau hai ngày thì lượng sữa còn lại chiếm:
\(1-\dfrac{1}{5}-\dfrac{1}{4}=1-\dfrac{9}{20}=\dfrac{11}{20}\)(hộp)
b: Lượng sữa còn lại sau 2 ngày là:
\(1000\cdot\dfrac{11}{20}=550\left(ml\right)\)
2N
1
22 tháng 12 2021
\(936-\left(4x+5x\right)=900\\ 936-9x=900\\ 9x=36\\ x=4\)
XA
3
18 tháng 8 2021
\(d,\dfrac{5}{7}+\dfrac{9}{23}+-\dfrac{12}{7}+\dfrac{14}{23}\)
\(=\left(\dfrac{5}{7}+\dfrac{-12}{7}\right)+\left(\dfrac{9}{23}+\dfrac{14}{23}\right)\)
\(=-\dfrac{7}{7}+\dfrac{23}{23}\)
\(=\left(-1\right)+1=0\)
\(e,\dfrac{3}{17}+-\dfrac{5}{13}+-\dfrac{18}{35}+\dfrac{14}{17}+\dfrac{17}{-35}+-\dfrac{8}{13}\)
\(=\left(\dfrac{3}{17}+\dfrac{14}{17}\right)+\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{-18}{35}+\dfrac{-17}{35}\right)\)
\(=\dfrac{17}{17}+\dfrac{-13}{13}+-\dfrac{35}{35}\)
\(=1+\left(-1\right)+\left(-1\right)=0+\left(-1\right)=-1\)
\(f,\dfrac{-3}{8}. \dfrac{1}{6}+\dfrac{3}{-8}.\dfrac{5}{6}+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}.\dfrac{1}{6}+\dfrac{-3}{8}.\dfrac{5}{6}+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}.\left(\dfrac{1}{6}+\dfrac{5}{6}\right)+-\dfrac{10}{16}\)
=\(\dfrac{-3}{8}.1+\dfrac{-10}{16}\)
\(=\dfrac{-3}{8}+\dfrac{-10}{16}\)
\(=\dfrac{-6}{16}+\dfrac{-10}{16}=\dfrac{-16}{16}=-1\)
\(g,\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{11}{-4}=\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{-11}{4}\)
\(=\left(\dfrac{-4}{11}.\dfrac{-11}{4}\right).\dfrac{5}{15}\)
\(=1.\dfrac{5}{15}=1.\dfrac{1}{3}=\dfrac{1}{3}\)
\(h,\dfrac{7}{36}-\dfrac{8}{-9}+\dfrac{-2}{3}=\dfrac{7}{36}-\dfrac{-8}{9}+\dfrac{-2}{3}\)
\(=\dfrac{7}{36}-\dfrac{-32}{36}+\dfrac{-24}{36}=\dfrac{7-\left(-32\right)+\left(-24\right)}{36}\)
\(=\dfrac{15}{56}=\dfrac{5}{12}\)
Tick mình nha ^^
18 tháng 8 2021
d.\(\dfrac{5}{7}\)+\(\dfrac{9}{23}\)+\(\dfrac{12}{7}\)+\(\dfrac{14}{23}\)=(\(\dfrac{5}{7}\)+\(\dfrac{12}{7}\))+(\(\dfrac{9}{23}\)+\(\dfrac{14}{23}\))
=\(\dfrac{17}{7}\)+ 1 = \(\dfrac{24}{7}\)
e.\(\dfrac{3}{17}\)+\(\dfrac{-5}{13}\)+\(\dfrac{-18}{35}\)+\(\dfrac{14}{17}\)+\(\dfrac{17}{-35}\)+\(\dfrac{-8}{13}\)
=(\(\dfrac{3}{17}\)+\(\dfrac{14}{17}\))+(\(\dfrac{-5}{13}\)+\(\dfrac{-8}{13}\))+(\(\dfrac{-18}{35}\)+\(\dfrac{17}{-35}\))
= 1+ (-1) + (-1) = -1
f. \(\dfrac{-3}{8}\).\(\dfrac{1}{6}\)+\(\dfrac{3}{-8}\).\(\dfrac{5}{6}\)+\(\dfrac{-10}{16}\)=\(\dfrac{-3}{8}\)(\(\dfrac{1}{6}\)+\(\dfrac{5}{6}\)) + \(\dfrac{-5}{8}\)
=\(\dfrac{-3}{8}\)+\(\dfrac{-5}{8}\)= -1
g. \(\dfrac{-4}{11}\).\(\dfrac{5}{15}\).\(\dfrac{11}{-4}\)=\(\dfrac{5}{15}\)
h.\(\dfrac{7}{36}\)-\(\dfrac{8}{-9}\)+\(\dfrac{-2}{3}\)= \(\dfrac{7}{36}\)-\(\dfrac{-32}{36}\)+\(\dfrac{-24}{36}\)
=\(\dfrac{-49}{36}\)
XA
2
21 tháng 8 2021
a. x : 13/16 = 5/-8
x : 13/16 = -5/8
x = -5/8 . 13/16
x = -65/128
21 tháng 8 2021
b.
x . \(\dfrac{-14}{28}\) = \(\dfrac{6}{-9}\) - \(\dfrac{2}{15}\)
x . \(\dfrac{-14}{28}\) = \(\dfrac{-9}{6}\) - \(\dfrac{2}{15}\)
x . \(\dfrac{-14}{28}\) = \(\dfrac{-49}{30}\)
x = \(\dfrac{-49}{30}\) : \(\dfrac{-14}{28}\)
x = \(\dfrac{-49}{30}\) . \(\dfrac{-28}{14}\)
x = \(\dfrac{-49}{15}\)
DT
1
NN
1
17 tháng 12 2021
\(\Leftrightarrow n+1\in\left\{1;-1;3;-3\right\}\)
hay \(n\in\left\{0;-2;2;-4\right\}\)
NM
2
24 tháng 7 2017
Ta có: 2a+a=3b
\(\Rightarrow\)a(2+1)=3b
\(\Rightarrow\)3a=3b
\(\Rightarrow\)a=b
NT
1
UI
2
17 tháng 1 2016
ta thấy 1008 chia hết cho 2;2y chia hết cho 2 nên 1003x chia hết cho 2, mà(1003;2)=1 nên x chia hết cho 2, x chẵn
để có x,y thuộc N thì 1003x<=2008=>x thuôc{0;1;2}
mà x chẵn nên x thuộc{0;2}
với x=0=>1003x+2y=0+2y=2008
=>2y=2008:2=1004
=>x=0;y=1004
với x=2 thì 1003x+2y=2008=1003.2+2y=2008=>2006+2y=2008=>2y=2=>y=1
=>x=2;y=1
vậy ta có các cặp số(x;y) là (0;1004);(2;1)
tick nha
= 250
Lấy mt ra
\(\left(-375\right)+625=250\)