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a) = 1/2 - 1/2 + 1/3 -1/3 + 1/4 - 1/4 + 1/5 - 1/5 + 1/6
= 0 + 0 + 0 + 0 + 1/6
= 1/6
b) 2/3 + 2/4 - 2/4 + 2/5 - 2/5 + 2/6 - 2/6 + 2/7 - 2/7 + 28
= 2/3 + 28
= 86/3
[tick cho mik nha]
a) \(1+\dfrac{4}{9}=\dfrac{9}{9}+\dfrac{4}{9}=\dfrac{9+4}{9}=\dfrac{13}{9}\)
b) \(5+\dfrac{1}{2}=\dfrac{10}{2}+\dfrac{1}{2}=\dfrac{10+1}{2}=\dfrac{11}{2}\)
c) \(3-\dfrac{5}{6}=\dfrac{18}{6}-\dfrac{5}{6}=\dfrac{18-5}{6}=\dfrac{13}{6}\)
d) \(\dfrac{31}{7}-2=\dfrac{31}{7}-\dfrac{14}{7}=\dfrac{31-14}{7}=\dfrac{17}{7}\)
\(\dfrac{1}{3}+\dfrac{3}{4}+\dfrac{1}{2}=\dfrac{4}{12}+\dfrac{9}{12}+\dfrac{6}{12}=\dfrac{19}{12}\)
\(\dfrac{6}{8}+\dfrac{2}{4}+\dfrac{6}{24}=\dfrac{3}{4}+\dfrac{2}{4}+\dfrac{1}{4}=\dfrac{6}{4}=\dfrac{3}{2}\)
\(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{5}{6}=\dfrac{3}{6}+\dfrac{2}{6}+\dfrac{5}{6}=\dfrac{10}{6}=\dfrac{5}{3}\)
\(\dfrac{3}{5}+\dfrac{3}{2}+2=\dfrac{6}{10}+\dfrac{15}{10}+\dfrac{20}{10}=\dfrac{41}{10}\)
\(\dfrac{1}{3}+\dfrac{3}{4}+\dfrac{1}{2}=\dfrac{13}{12}+\dfrac{1}{2}=\dfrac{19}{12}\\ \dfrac{6}{8}+\dfrac{2}{4}+\dfrac{6}{24}=\dfrac{5}{4}+\dfrac{6}{24}=\dfrac{3}{2}\\ \dfrac{1}{2}+\dfrac{1}{3}+\dfrac{5}{6}=\dfrac{5}{6}+\dfrac{5}{6}=\dfrac{10}{6}\\ \dfrac{3}{5}+\dfrac{3}{2}+2=\dfrac{21}{10}+\dfrac{20}{10}=\dfrac{41}{10}\)
1.
a, Ta có 28=14⇒14+56=1312(Bn tự quy đồng lên nhé !)
b,Ta có1216=34⇒18+34=78(Bn tự quy đồng lên nhé !)
c,Ta có636=16⇒14+16=512(Bn tự quy đồng lên nhé !)
d,Ta có1218=23⇒23+14=1112(Bn tự quy đồng lên nhé !)
7.Phần này mk chỉ cho đáp án thuia.67 ;
b,420=15 ;
c,615 ;
d,129
\(\frac{1}{2}\times\frac{1}{4}\div\frac{1}{6}=\frac{1}{2}\times\frac{1}{4}\times\frac{6}{1}=\frac{6}{8}=\frac{3}{4}.\)
\(\frac{1}{2}\)x \(\frac{1}{4}\) : \(\frac{1}{6}\) = \(\frac{1x1}{2x4}\) : \(\frac{1}{6}\) = \(\frac{1}{8}\) : \(\frac{1}{6}\) = \(\frac{1}{8}\)x \(\frac{6}{1}\)= \(\frac{1x6}{8x1}\) = \(\frac{6}{8}\) = \(\frac{3}{4}\)