9а^2-1/9a^2+6a+1
упростите

[tex] \frac{ 9a^{2}-1 }{9 a^{2}+6a+1 }= \frac{(3a+1)(3a-1)}{(3a+1)^2} = \frac{3a-1)}{3a+1} [/tex]