а)

[tex] \frac{ {p}^{2} + pc }{pb} = \frac{p(p + c)}{pb} = \frac{p + c}{b} [/tex]

б)

[tex] \frac{ {a}^{2} }{ {a}^{2} - 3a} = \frac{ {a}^{2} }{a(a - 3)} = \frac{a}{a - 3} [/tex]

в)

[tex] \frac{ {x}^{2} - 9 {y}^{2} }{x + 3y} = \frac{(x - 3y)(x + 3y)}{x + 3y} = x - 3[/tex]

г)

[tex] \frac{ {a}^{2} + 3a }{ {a}^{2} - 9 } = \frac{a(a + 3)}{(a - 3)(a + 3)} = \frac{a}{a - 3} [/tex]

д)

[tex] \frac{ {x}^{2} - 6xy + 9 {y}^{2} }{ {x}^{2} - 9 {y}^{2} } = \frac{(x - 3y)(x - 3y)}{(x - 3y)(x + 3y)} = \frac{x - 3y}{x + 3y} [/tex]