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\(4\dfrac{3}{8}+5\dfrac{2}{3}=\dfrac{4\times8+3}{8}+\dfrac{5\times3+2}{3}\\ =\dfrac{35}{8}+\dfrac{17}{3}=\dfrac{35\times3+17\times8}{24}=\dfrac{241}{24}\\ ----\\ 2\dfrac{3}{8}+1\dfrac{1}{4}=\dfrac{2\times8+3}{8}+\dfrac{1\times4+1}{4}=\dfrac{19}{8}+\dfrac{5}{4}\\ =\dfrac{19+5\times2}{8}=\dfrac{29}{8}\\ ----\\ 2\dfrac{3}{8}-1\dfrac{1}{4}+5\dfrac{1}{3}=\left(2-1+5\right)+\left(\dfrac{3}{8}-\dfrac{1}{4}+\dfrac{1}{3}\right)\\ =6+\dfrac{3\times3-1\times6+1\times8}{24}\\ =6+\dfrac{11}{24}=6\dfrac{11}{24}\)
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Bài làm :
Ta có :
\(\frac{3}{4}\times\frac{1}{8}+\frac{3}{4}\times\frac{3}{8}-\frac{1}{2}\times\frac{3}{4}\)
\(=\frac{3}{4}\times\left(\frac{1}{8}+\frac{3}{8}-\frac{1}{2}\right)\)
\(=\frac{3}{4}\times0=0\)
Chúc bạn học tốt !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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\(\left(\frac{4}{5}.\frac{3}{8}+\frac{4}{5}.\frac{5}{8}-\frac{4}{5}.\frac{7}{8}\right):\frac{1}{2}\)
= \(\frac{4}{5}.\left(\frac{3}{8}+\frac{5}{8}-\frac{7}{8}\right):\frac{1}{2}\)
= \(\frac{4}{5}.\frac{1}{8}:\frac{1}{2}\)
= \(\frac{1}{5}\)
= 0,2
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a: 4A=4+4^2+...+4^9
=>3A=4^9-1
=>A=(4^9-1)/3
b: 2A=1+1/2+...+1/2^7
=>A=1-1/256=255/256
c: =1-1/5+1/5-1/9+...+1/85-1/89
=1-1/89=88/89
d: =1/3(3/1*4+3/4*7+...+3/304*307)
=1/3(1-1/4+1/4-1/7+...+1/304-1/307)
=1/3*306/307=102/307
e: E=1-1/2+1/2-1/3+...+1/11-1/12
=1-1/12=11/12
g: =2/5(1-1/6+1/6-1/11+...+1/96-1/101)
=2/5*100/101=40/101
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\(\frac{1}{6}:\frac{4}{5}+\frac{1}{8}:\frac{4}{5}=\left(\frac{1}{6}+\frac{1}{8}\right):\frac{4}{5}=\left(\frac{4}{24}+\frac{3}{24}\right).\frac{5}{4}=\frac{7}{24}.\frac{5}{4}=\frac{35}{96}\)
\(\frac{1}{6}:\frac{4}{5}-\frac{1}{8}:\frac{4}{5}=\left(\frac{1}{6}-\frac{1}{8}\right):\frac{4}{5}=\left(\frac{4}{24}-\frac{3}{24}\right).\frac{5}{4}=\frac{1}{24}.\frac{5}{4}=\frac{5}{96}\)
a) 1/6 : 4/5 + 1/8 : 4/5 b) 1/6 : 4/5 - 1/8 : 4/5
= 4/5 : ( 1/6 + 1/8 ) = 4/5 : ( 1/6 - 1/8 )
= 4/5 : 7/24 = 4/5 : 1/24
= 96/35 = 96/5
1/4 = 0,25
4/8 = 0,5