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b. \(\dfrac{5}{2}=\dfrac{5.5}{2.5}=\dfrac{25}{10}=2,5\)
\(\dfrac{37}{25}=\dfrac{37.4}{25.4}=\dfrac{148}{100}=1,48\)
\(\dfrac{49}{50}=\dfrac{49.2}{50.2}=\dfrac{98}{100}=0,98\)
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21x - 5.2 + 3 - 7 = 7x
=> 21x - 10 - 4 = 7x
=> 2x - 14 = 7x
=> 2x - 7x = 14
=> -5x = 14
=> x = -14/5
Vậy...
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\(3\frac{2}{5}\times2\frac{1}{7}\)
\(=\frac{17}{5}\times\frac{15}{7}\)
\(=\frac{17\times15}{5\times7}\)
\(=\frac{17\times3\times5}{5\times7}\)
\(=\frac{17\times3}{7}\)
\(=\frac{51}{7}\)
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21x - 5.2 + 3 - 7 = 7x
=> 21x - 10 - 4 = 7x
=> 21x - 14 = 7x
=> 21x - 7x = 14
=> 14x = 14
=> x = 14 : 14
=> x = 1
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\(a,\frac{2}{5}:\frac{6}{5}+\frac{3}{4}.\frac{12}{5}\)
=\(\frac{2}{5}.\frac{5}{6}+\frac{9}{5}\)
=\(\frac{1}{3}+\frac{9}{5}\)
=\(\frac{32}{5}\)
b) \(\frac{17}{5}.\frac{3}{5}.\frac{17}{5}.\frac{2}{5}\)
=\(\frac{17}{5}.\left(\frac{3}{5}.\frac{2}{5}\right)\)
=\(\frac{17}{5}.\frac{6}{25}\)
=\(\frac{102}{125}\)
c)\(\frac{1}{4}+\frac{3}{4}.\frac{2}{3}-\frac{1}{2}\)
=\(\frac{1}{4}+\frac{1}{2}-\frac{1}{2}\)
=\(\frac{1}{4}\)
d)\(\frac{6}{7}+\frac{5}{8}:5\)
=\(\frac{6}{7}+\frac{5}{8}.\frac{1}{5}\)
=\(\frac{6}{7}+\frac{1}{8}\)
=\(\frac{48}{56}+\frac{7}{56}\)
=\(\frac{55}{56}\)
tk nhé bn!
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3/4+2/3+5/12=11/6
7/8-7/16-11/32=3/32
3/5*2/7*5/6=1/7
15/16:3/8:3/4=10/3
bạn nhé
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\(A=\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{11}-\frac{1}{14}\)
\(A=\frac{1}{2}-\frac{1}{14}\)
\(A=\frac{3}{7}\)
\(A=\)\(\frac{3}{5\times2}+\frac{3}{5\times8}+\frac{3}{8\times11}+...+\frac{3}{11\times14}\)
\(=\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+...+\frac{1}{11}-\frac{1}{14}\)
\(=\frac{1}{2}-\frac{1}{14}\)
\(=\frac{3}{7}\)
13/5 x 2/3 + 7/3 x 2/3 = (13/5 + 7/3) x 2/3 = 74/15 x 2/3=28/5