40/4 - | 11/4 + 4/3 ]
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17 tháng 9 2023
\(a,\dfrac{1}{12}\times\dfrac{4}{5}=\dfrac{1\times4}{12\times5}=\dfrac{1}{15}\)
\(b,\dfrac{40}{7}\times\dfrac{21}{5}=\dfrac{40\times21}{7\times5}=\dfrac{24}{1}=24\)
\(c,\dfrac{9}{5}\div\dfrac{4}{7}=\dfrac{9}{5}\times\dfrac{7}{4}=\dfrac{9\times7}{5\times4}=\dfrac{63}{20}\)
\(d,\dfrac{11}{24}\div\dfrac{44}{3}=\dfrac{11}{24}\times\dfrac{3}{44}=\dfrac{11\times3}{24\times44}=\dfrac{1}{32}\)
LQ
0
21 tháng 2 2022
b: \(B=\dfrac{5}{2}-\dfrac{7}{2}+\dfrac{3}{8}+\dfrac{6}{8}+\dfrac{-6}{11}-\dfrac{5}{11}=-2-1+\dfrac{9}{8}=\dfrac{9}{8}-3=-\dfrac{15}{8}\)
c: \(C=\left(\dfrac{4}{3}+\dfrac{7}{3}+\dfrac{1}{3}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)=4+1=5\)
d: \(D=\dfrac{4}{19}\left(\dfrac{-5}{6}-\dfrac{7}{12}\right)-\dfrac{40}{57}\)
\(=\dfrac{4}{19}\cdot\dfrac{-17}{12}-\dfrac{40}{57}=-1\)
e: \(E=\dfrac{1}{3}\left(\dfrac{4}{5}-\dfrac{9}{5}\right)+\dfrac{2}{3}=\dfrac{2}{3}-\dfrac{1}{3}=\dfrac{1}{3}\)
14 tháng 8 2023
a) \(...\Rightarrow x.\left(2+5\right)=14\Rightarrow x.7=14\Rightarrow x=14:7=2\)
b) \(...\Rightarrow x.\left(9+1\right)=20\Rightarrow x.10=20\Rightarrow x=20:10=2\)
c) \(...\Rightarrow x.\left(\dfrac{2}{3}+\dfrac{1}{3}\right)=1999\Rightarrow x.\dfrac{3}{3}=1999\Rightarrow x=1999\)
d) \(...\Rightarrow11.x+22=5.x+40\Rightarrow11.x-5.x=40-22\Rightarrow6.x=18\Rightarrow x=18:6=3\)
e) \(...\Rightarrow11.x-66=4.x+11\Rightarrow11.x-4.x=11+66\Rightarrow7.x=77\Rightarrow x=77:7=11\)
f) \(...\Rightarrow\left(3.x-12\right):x=12-10\)
\(\Rightarrow3.x-12=2.x\)
\(\Rightarrow3.x-2.x=12\)
\(\Rightarrow x=12\)
g) \(...\Rightarrow\left(5.x+7\right):x=26-20\)
\(\Rightarrow5.x+7=6.x\)
\(\Rightarrow6.x-5.x=7\)
\(\Rightarrow x=7\)
h) \(...\Rightarrow x.\left(1999-1\right)=1999.\left(1997+1\right)\)
\(\Rightarrow x.1998=1999.1998\)
\(\Rightarrow x=1999.1998:1998\)
\(\Rightarrow x=1999\)
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
14 tháng 8 2023
a, \(x\times\) 2 + \(x\times\) 5 = 14
\(x\) \(\times\) ( 2 + 5) = 14
\(x\) \(\times\) 7 = 14
\(x\) = 14: 7
\(x\) = 2
b, \(x\times9\) + \(x\)= 20
\(x\) \(\times\)( 9 + 1) = 20
\(x\) \(\times\) 10 = 20
\(x\) = 2
c, \(x\) : \(\dfrac{3}{2}\) + \(x\times\dfrac{1}{3}\) = 1999
\(x\times\) \(\dfrac{2}{3}\) + \(x\) \(\times\dfrac{1}{3}\) = 1999
\(x\times\) ( \(\dfrac{2}{3}\) + \(\dfrac{1}{3}\)) = 1999
\(x\) = 1999
d, 11\(\times\)(\(x+2\)) = 5 \(\times\) \(x\) + 40
11 \(\times\) \(x\) + 22 = 5 \(\times\) \(x\) + 40
11 \(\times\) \(x\) = 5 \(\times\) \(x\) + 40 - 22
11 \(\times\) \(x\) = 5 \(\times\) \(x\) + 18
11 \(\times\) \(x\) - 5 \(\times\) \(x\) = 18
\(x\) \(\times\) ( 11 - 5) = 18
\(x\) \(\times\) 6 = 18
\(x\) = 3
TV
4
TN
22 tháng 7 2016
1)C= 1/5+1/10+1/20+1/40+...+1/1280
\(=\frac{1}{5}\left(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^8}\right)\)
Đặt cái trong ngoặc là A ta có:\(2A=2+1+...+\frac{1}{2^7}\)
\(2A-A=\left(2+1+...+\frac{1}{2^7}\right)-\left(1+\frac{1}{2}+...+\frac{1}{2^8}\right)\)
\(A=2-\frac{1}{2^8}\).Thay A vào ta được:\(C=\frac{1}{5}\left(2-\frac{1}{2^8}\right)=\frac{1}{5}\cdot\frac{511}{256}=\frac{511}{1280}\)
2)D= 2/1*3+2/3*5+2/5*10+2/7*9+2/9*11+2/11*18+2/13*15
\(=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{13}-\frac{1}{15}\)
\(=1-\frac{1}{15}\)
\(=\frac{14}{15}\)
3)E= 4/3*7+4/7*11+4/11*15+4/15*19+4/19*23+4/23*27
\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+...+\frac{1}{23}-\frac{1}{27}\)
\(=\frac{1}{3}-\frac{1}{27}\)
\(=\frac{8}{27}\)
4)G= 1/2+1/6+1/12+1/20+1/30+1/42+...+1/110
\(=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{10.11}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{10}-\frac{1}{11}\)
\(=1-\frac{1}{11}\)
\(=\frac{10}{11}\)
5)H= 3/1*2+3/2*3+3/3*4+3/4*5+...+3/9*10
\(=3\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=3\left(1-\frac{1}{10}\right)\)
\(=3\times\frac{9}{10}\)
\(=\frac{27}{10}\).Lần sau bạn đăng ít một thôi nhé
8 tháng 11 2018
chúc bạn học tốt !
chúc bạn học tốt !
chúc bạn học tốt !
chúc bạn học tốt !
HP
23 tháng 5 2022
\(\left(0,125+40\%-\dfrac{3}{40}\right):\left[11\dfrac{3}{7}+8\dfrac{1}{2}-\left(\dfrac{13}{12}-5\dfrac{4}{7}\right)\right]\)
\(=\left(\dfrac{1}{8}+\dfrac{2}{5}-\dfrac{3}{40}\right):\left[\dfrac{80}{7}+\dfrac{17}{2}-\left(\dfrac{13}{12}-\dfrac{39}{7}\right)\right]\)
\(=\dfrac{9}{20}:\dfrac{293}{12}\)
\(=\dfrac{27}{1465}\)
7 tháng 9 2016
a) i don't know
b) \(\frac{5}{1.2}+\frac{5}{2.3}+\frac{5}{3.4}+...+\frac{5}{28.29}\)
\(5.\left(1-\frac{1}{2}\right)+5.\left(\frac{1}{2}-\frac{1}{3}\right)+5.\left(\frac{1}{3}-\frac{1}{4}\right)+...+5.\left(\frac{1}{28}-\frac{1}{29}\right)\)
\(5.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{28}-\frac{1}{29}\right)\)
\(5.\left(1-\frac{1}{29}\right)\)
\(5.\frac{28}{29}\)
\(\frac{140}{29}\)
7 tháng 9 2016
c ) \(\frac{4}{2.4}+\frac{4}{4.6}+...+\frac{4}{28.30}\)
\(2.\left(\frac{1}{2}-\frac{1}{4}\right)+2.\left(\frac{1}{4}-\frac{1}{6}\right)+...+2.\left(\frac{1}{28}-\frac{1}{30}\right)\)
\(2.\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{28}-\frac{1}{30}\right)\)
\(2.\left(\frac{1}{2}-\frac{1}{30}\right)\)
\(2.\frac{7}{15}=\frac{14}{15}\)
d) đề là thế này nè : 4/6 + 4/12 + 4/20 + 4/30 + 4/42 + 4/56
4/2.3 + 4/3.4 + 4/4.5 + 4/5.6 + 4/6.7 + 4/7.8
4.(1/2-1/3) + 4.(1/3-1/4 ) + 4.(1/4-1/5) + 4.(1/5-1/6 ) + 4.(1/6 - 1/7 ) + 4.(1/7-1/8 )
4.(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8)
4.(1/2-1/8)
4.1/16
1/4
\(=10-\dfrac{11}{4}-\dfrac{4}{3}=\dfrac{71}{12}\)
\(\dfrac{40}{4}-\left|\dfrac{11}{4}+\dfrac{4}{3}\right|\\ =10-\dfrac{49}{12}\\ =\dfrac{120}{12}-\dfrac{49}{12}\\ =\dfrac{71}{12}\)