Bonsoir,
a) [tex]\dfrac{8}{5}-\dfrac{4}{15}-\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{8\times3}{5\times3}-\dfrac{4}{15}-\dfrac{1\times3}{5\times3}-\dfrac{1\times5}{3\times5}[/tex]
[tex]\dfrac{8}{5}-\dfrac{4}{15}-\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{24}{15}-\dfrac{4}{15}-\dfrac{3}{15}-\dfrac{5}{15}\\\\\dfrac{8}{5}-\dfrac{4}{15}-\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{12}{15}\\\\\dfrac{8}{5}-\dfrac{4}{15}-\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{3\times4}{3\times5}\\\\\dfrac{8}{5}-\dfrac{4}{15}-\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{4}{5}[/tex]
On procède de la même manière pour les suivants.
[tex]b)\ \dfrac{5}{6} - \dfrac{5}{12} + \dfrac{19}{12} - \dfrac{1}{6}=\dfrac{10}{12} - \dfrac{5}{12} + \dfrac{19}{12} - \dfrac{2}{12}=\dfrac{22}{12}=\dfrac{11}{6}\\\\c)\ \dfrac{24}{21}+\dfrac{8}{7} -\dfrac{20}{21}-\dfrac{1}{3}=\dfrac{24}{21}+\dfrac{24}{21} -\dfrac{20}{21}-\dfrac{7}{21}=\dfrac{21}{21}=1\\\\d)\ \dfrac{28}{13}-\dfrac{5}{26}+\dfrac{23}{26}+\dfrac{2}{13}=\dfrac{56}{26}-\dfrac{5}{26}+\dfrac{23}{26}+\dfrac{4}{26}=\dfrac{78}{26}=3
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