Răspuns:
b)
Explicație pas cu pas:
[tex]\frac{5a + 2b}{7a + 2b} = \frac{4}{5} \\ 5(5a + 2b) = 4(7a + 2b) \\ 25a + 10b = 28a + 8b \\ 3a = 2b = k \iff b = \frac{3a}{2} [/tex]
[tex]\frac{2a - b}{a + b} = \frac{2a - \frac{3a}{2}}{a + \frac{3a}{2} } = \frac{4a - 3a}{2a + 3a} = \frac{a}{5a} = \bf \frac{1}{5} \\ [/tex]
