b)
[tex] \frac{3 {a}^{2} - 9a}{ {a}^{2} - 9} = \frac{3a(a - 3)}{(a + 3)(a - 3)} = \frac{3a}{a + 3} [/tex]
c)
[tex] \frac{ {y}^{2} - 3yz -4 {z}^{2} }{3 {y}^{2} - 12yz } = \frac{(y + z)(y - 4z)}{3y(y - 4z)} = \frac{y + z}{3y} [/tex]
d)
[tex] \frac{ {d}^{2} + 4d + 4}{ {d}^{2} + 2d} = \frac{(d + 2)(d + 2)}{d(d + 2)} = \frac{d + 2}{d} [/tex]
e)
[tex] \frac{5f - 15}{3 {f}^{2} - 13f + 12} = \frac{5(f - 3)}{(3f - 4)(f - 3)} = \frac{5}{3f - 4} [/tex]
I hope I helped you^_^
