4/9a - (5/9a - 4b) = 4/9a - 5/9a + 4b
Подобные слагаемые: 4/9a и -5/9a
4/9a - 5/9a + 4b = (4 - 5)/9a + 4b4/9a - 5/9a + 4b = -1/9a + 4b
4/9a - (5/9a - 4b) = 4/9a - 5/9a + 4b
Подобные слагаемые: 4/9a и -5/9a
4/9a - 5/9a + 4b = (4 - 5)/9a + 4b
4/9a - 5/9a + 4b = -1/9a + 4b