Réponse:
A=
[tex] \frac{1}{2} - \frac{3}{4} \div \frac{9}{8} = \frac{1}{2} - \frac{3 \times 8}{4 \times 9} = \frac{1}{2} - \frac{3 \times 2 \times2 \times 2}{2\times 2 \times 3 \times 3} = \frac{1}{2} - \frac{2}{3} = \frac{3}{6} - \frac{4}{6} = \frac{ - 1}{6} [/tex]
B=
[tex]( \frac{1}{2} - \frac{3}{4} ) \times \frac{8}{9} = ( \frac{2}{4} - \frac{3}{4} )\times \frac{8}{9} = \\ \frac{ - 1}{4} \times \frac{8}{9} = \frac{ - 1 \times 4 \times 4}{4 \times 9} = \\ \frac{ - 4}{9} [/tex]
