Ответ:

номер 4

1.

[tex] \frac{5}{x(x - 1)} = \frac{5}{ {x}^{2} - x} [/tex]

2.

[tex] \frac{2a}{a + 2} + \frac{1}{a - 3} = \frac{2 {a}^{2} - 5a + 2}{ {a}^{2} - a - 6} [/tex]

номер 7

[tex] \frac{2b}{b - 4} + \frac{b}{b + 4} + \frac{2 {b}^{2} }{16 - {b}^{2} } = \frac{b}{b - 4} [/tex]