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=(1-1/2)(1+1/2)*...*(1+1/10)(1-1/10)
=1/2*2/3*...*9/10*3/2*4/3*...*11/10
=1/10*11/2
=11/20
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\(\frac{4}{3}\times\frac{9}{8}\times...\times\frac{81}{80}=\frac{2^2}{1\times3}\times\frac{3^2}{2\times4}\times...\times\frac{9^2}{8\times10}\)
\(=\frac{2\times3\times4\times...\times9}{1\times2\times3\times...\times8}\times\frac{2\times3\times4\times...\times9}{3\times4\times5\times...\times10}\\ =\frac{9}{1}\times\frac{2}{10}=\frac{9}{5}\)
4/3.9/8.16/15.25/24.36/35.49/48.64/63.81/80
=3/2.16/15.25/24.36/35.49/48.64/63.81/80
=5/3.36/35.49/48.64/63.81/80
=7/4.64/63.81/80
=9/5
+
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1/10 + 4/20 + 9/30 + 16/40 + 25/50 + 36/60 + 49/70 + 64/80 + 81/90
= 1/10 + 2/10 + 3/10 + 4/10 + 5/10 + 6/10 + 7/10 + 8/10 + 9/10
=(1+2+3+....+9) /10
=(1+9)x9:2 /10
=45/10=4,5
chắc chắn đúng đó
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\(\frac{10}{25};\frac{14}{18};\frac{15}{20};\frac{16}{40};\frac{30}{48};\frac{63}{81}\)
\(=>\frac{10}{25}=\frac{2}{5}\)\(;\frac{14}{18}=\frac{7}{9};\frac{15}{20}=\frac{3}{4};\frac{16}{40}=\frac{2}{5};\frac{30}{48}=\frac{5}{8};\frac{63}{81}=\frac{7}{9}\)
\(=>\frac{2}{5};\frac{7}{9};\frac{3}{4};\frac{2}{5};\frac{5}{8};\frac{7}{9}\)
Phân số bằng nhau là : \(\frac{10}{25};\frac{16}{40}\)và \(\frac{14}{18};\frac{63}{81}\)
\(\frac{10}{15}=\frac{2}{3}\) \(\frac{14}{18}=\frac{7}{9}\) \(\frac{15}{20}=\frac{3}{4}\)
\(\frac{16}{40}=\frac{2}{5}\) \(\frac{36}{48}=\frac{3}{4}\) \(\frac{63}{81}=\frac{7}{9}\)
Vậy các phân số bằng nhau là :
\(\frac{15}{20}=\frac{36}{48}\) ; \(\frac{14}{18}=\frac{63}{81}\)
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\(\dfrac{1}{10}+\dfrac{4}{20}+\dfrac{9}{30}+\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
\(=\dfrac{1}{10}+\dfrac{1}{5}+\dfrac{3}{10}+\dfrac{2}{5}+\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{7}{10}+\dfrac{4}{5}+\dfrac{9}{10}\)
\(=\left(\dfrac{1}{10}+\dfrac{3}{10}+\dfrac{7}{10}+\dfrac{9}{10}\right)+\left(\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}\right)+\dfrac{1}{2}\)
\(=2+2+\dfrac{1}{2}\)
\(=4+\dfrac{1}{2}\)
\(=\dfrac{8}{2}+\dfrac{1}{2}=\dfrac{9}{2}\)
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=1/10+1/10+3/10+4/10+5/10+6/10+7/10+8/10+9/10
=1/10+45/10
=46/10=23/5
TL
\(\frac{100}{25}-\frac{36}{25}=4-\frac{36}{25}\)=\(\frac{64}{25}\)
NHA BN
HT
\(\frac{100}{25}-\frac{36}{81}=4-\frac{4}{9}=3\frac{5}{9}\)
@muối