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Bài 2:
a) \(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)...\left(1-\frac{1}{2018}\right)\))
\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{2017}{2018}=\frac{1}{2018}\)
Bài 1 thì mk ko bk, xl bn nha!
A) 7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11
=7/38.(9/11+4/11-2/11)
=7/38
B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20
=5/31.(21/25-7/10-9/20)
=5/31.(-31/100)
=-1/20
A = ( -4/5 + 4/3 ) + (-5/4 + 14/5) - 7/3
= 8/15 + 31/20 - 7/3
= 25/12 - 7/3
= -1/4
B = 8/3 x 2/5 x 3/8 x 10x 19/92
= 16/15 x 15/4 x 19/92
= 4x19/92
= 19/23
C = - \(\dfrac{5}{7}\) x \(\dfrac{2}{11}\) + \(\dfrac{-5}{7}\) x \(\dfrac{9}{14}\) + \(\dfrac{1}{57}\)
= - \(\dfrac{10}{77}\) - \(\dfrac{45}{98}\) + \(\dfrac{1}{57}\)
= - \(\dfrac{635}{1078}\) + \(\dfrac{1}{57}\)
= - \(\dfrac{36195}{61446}\) + \(\dfrac{1078}{61446}\)
= - \(\dfrac{35117}{61446}\)
a; - \(\dfrac{10}{13}\) + \(\dfrac{5}{17}\) - \(\dfrac{3}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{11}{20}\)
= - (\(\dfrac{10}{13}\) + \(\dfrac{3}{13}\)) + (\(\dfrac{5}{17}\) + \(\dfrac{12}{17}\)) - \(\dfrac{11}{20}\)
= - 1 + 1 - \(\dfrac{11}{20}\)
= 0 - \(\dfrac{11}{20}\)
= - \(\dfrac{11}{20}\)
b; \(\dfrac{3}{4}\) + \(\dfrac{-5}{6}\) - \(\dfrac{11}{-12}\)
= \(\dfrac{9}{12}\) - \(\dfrac{10}{12}\) + \(\dfrac{11}{12}\)
= \(\dfrac{10}{12}\)
= \(\dfrac{5}{6}\)
c; [13.\(\dfrac{4}{9}\) + 2.\(\dfrac{1}{9}\)] - 3.\(\dfrac{4}{9}\)
= [\(\dfrac{52}{9}\) + \(\dfrac{2}{9}\)] - \(\dfrac{4}{3}\)
= \(\dfrac{54}{9}\) - \(\dfrac{4}{3}\)
= \(\dfrac{14}{3}\)
a. 37-7.(x+1)=40-8.3
37 - 7(x+1) = 16
7(x+1) = 21
x+1 = 3
x=2
b. (x+5).3=11=10+(3+4).4
(sao có 2 dấu bằng, dấu nào là dấu cộng do viết nhầm ???)
c. 25-5.3+4.10=100-5.x
50 = 100 - 5x
5x = 50
x=10
d. 36+2.(x-7)=12+8.(3+5)-36
36 + 2(x-7) = 40
2(x-7) = 4
x-7 =2
x=9
e. 3.(x+7)-9=11.5-5-8
3(x+7) - 9 = 42
3(x+7) = 51
x+7 = 17
x=10
1.
a,x+11/30=19/20
=> x=19/20-11/30
=> x=7/12
b,\(x:3\dfrac{1}{5}=1\dfrac{1}{2}\)
\(\Rightarrow x:\dfrac{16}{5}=\dfrac{3}{2}\)
\(\Rightarrow x=\dfrac{3}{2}\cdot\dfrac{16}{5}\)
\(\Rightarrow x=\dfrac{24}{5}\)
c, \(7\cdot x-3\cdot x=3,2\)
\(\Rightarrow x\left(7-3\right)=3,2\)
\(\Rightarrow4x=3,2\)
\(\Rightarrow x=3,2:4\)
\(\Rightarrow x=0,8\)
d, \(x\cdot13-x:\dfrac{1}{4}=36\)
\(\Rightarrow x\cdot13-x\cdot4=36\)
\(\Rightarrow x\left(13-4\right)=36\)
\(\Rightarrow12x=36\)
\(\Rightarrow x=36:12\)
\(\Rightarrow x=3\)
e,\(8,75\cdot x+1,25\cdot x=20\)
\(\Rightarrow x\left(8,75+1,25\right)=20\)
\(\Rightarrow10x=20\)
\(\Rightarrow x=20:10\)
\(\Rightarrow x=2\)
2.
a. \(\dfrac{3}{5}+25-\dfrac{1}{5}\)
\(=\left(\dfrac{3}{5}-\dfrac{1}{5}\right)+25\)
\(=\dfrac{2}{5}+25\)
\(=\dfrac{127}{5}=25,4\)
b. \(\dfrac{6}{7}:\dfrac{1}{2}\cdot\dfrac{3}{4}-\dfrac{5}{8}\)
\(=\dfrac{6}{7}\cdot2\cdot\dfrac{3}{4}-\dfrac{5}{8}\)
\(=\dfrac{12}{7}\cdot\dfrac{3}{4}-\dfrac{5}{8}\)
\(=\dfrac{9}{7}-\dfrac{5}{8}\)
\(=\dfrac{37}{56}\)
c,\(\left(1-\dfrac{1}{2}\right)\cdot\left(1-\dfrac{1}{3}\right)\cdot\left(1-\dfrac{1}{4}\right)\cdot\left(1-\dfrac{1}{5}\right)\)
\(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot\dfrac{3}{4}\cdot\dfrac{4}{5}\)
\(=\dfrac{1\cdot2\cdot3\cdot4}{2\cdot3\cdot4\cdot5}\)
\(=\dfrac{1}{5}\)
d. \(\dfrac{5932+6001\cdot5931}{5932\cdot6001-69}\)
\(=1\)