[tex]Bonjour;\\\\\\Exercice\ n\°\ 1\ .\\\\\\A=\dfrac{2}{9}-\dfrac{5}{9} \times\dfrac{7}{10} +\dfrac{5}{3}=\dfrac{2\times10}{9\times10}-\dfrac{5\times7}{9\times10} +\dfrac{5\times30}{3\times30}\\\\\\=\dfrac{20}{90}-\dfrac{35}{90} +\dfrac{150}{90}=\dfrac{20-35+150}{90}=\dfrac{135}{90}=\dfrac{3\times45}{2\times45}=\dfrac{3}{2}\ .[/tex]
[tex]B=\dfrac{4}{9}\times\dfrac{15}{28}-\dfrac{49}{15}\times\dfrac{25}{14}=\dfrac{4}{28}\times\dfrac{15}{9}-\dfrac{49}{14}\times\dfrac{25}{15}\\\\\\=\dfrac{4}{4\times7}\times\dfrac{3\times5}{3\times3}-\dfrac{7\times7}{2\times7}\times\dfrac{5\times5}{3\times5}\\\\\\=\dfrac{1}{7}\times\dfrac{5}{3}-\dfrac{7}{2}\times\dfrac{5}{3}=\dfrac{1\times5}{7\times3}-\dfrac{7\times5}{2\times3}=\dfrac{1\times5\times2}{7\times3\times2}-\dfrac{7\times5\times7}{2\times3\times7}\\\\\\=\dfrac{10}{42}-\dfrac{245}{42}[/tex]
[tex]=\dfrac{10-245}{42}=-\dfrac{235}{42}\ .[/tex]
