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\(A=\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+...+\dfrac{1}{13.14}\)
\(=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{13}-\dfrac{1}{14}\)
\(=\dfrac{1}{1}-\dfrac{1}{14}=\dfrac{13}{14}\)
Ta thấy: \(\dfrac{13}{14}< 1\)
Vậy A<1
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\(\frac{3}{13}+4\frac{7}{26}+1\frac{1}{12}=5+\left(\frac{3}{13}+\frac{7}{26}+\frac{1}{12}\right)=5\frac{7}{12}\)
\(\frac{2}{3}+\frac{4}{37}+5\frac{5}{11}=5+\left(\frac{2}{3}+\frac{4}{27}+\frac{5}{111}\right)\)ta thấy 2/3 > 7/12
Nên \(\frac{3}{13}+4\frac{7}{26}+1\frac{1}{2}\)< \(\frac{2}{3}+\frac{4}{37}+5\frac{5}{111}\)
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Bài 1:
a: -8/12<0<-3/-4
b: -56/24<0<7/3
c: 4/25<1<15/13
=>-4/25>-15/13
Bài 2:
a: =-60/45=-4/3
b: =4/15-3/2-8/5=8/30-45/30-48/30=-85/30=-17/6
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a: 14/5-7/5=7/5
b: 7/8-1/3+5/4
=21/24-8/24+30/24
=43/24
c; =7/6+5/6+2/15+13/15
=2+1
=3
d: =4*5/3*11=20/33
e: =2/9*1/6*1/4=2/9*1/24=1/108
2:
a: \(=\dfrac{3}{9}\cdot\dfrac{4}{4}\cdot\dfrac{5}{5}\cdot\dfrac{6}{6}\cdot\dfrac{7}{7}=\dfrac{1}{3}\)
b: \(=\dfrac{1}{6}\left(\dfrac{22}{3}-\dfrac{2}{3}\right)=\dfrac{10}{3}\cdot\dfrac{1}{6}=\dfrac{10}{18}=\dfrac{5}{9}\)
c; \(=\dfrac{1}{3}\left(9-\dfrac{2}{5}-\dfrac{3}{5}\right)=\dfrac{8}{3}\)