Sagot :
Réponse:
[tex]H = - 2 \div ( \frac{1}{3} + \frac{1}{9} ) \\ H = - 2 \div ( \frac{1 \times 3}{3 \times 3} + \frac{1}{9}) \\ H = - 2 \div ( \frac{3}{9} + \frac{1}{9} ) \\ H = - 2 \div \frac{4}{9 } \\ H = - 2 \times \frac{9}{4} \\ H = \frac{ - 2 \times 9}{2 \times 2} \\ H = - \frac{9}{2} [/tex]