Question

(a/a+1) / (1-3a²/1-a²)

Answer 1

$frac{frac{a}{a+1}}{frac{1-3a^2}{1-a^2}}=frac{a}{(a+1)}*frac{(1-a^2)}{(1-3a^2)}=frac{a(1-a^2)}{(a+1)(1-3a^2)}=frac{a(1-a)(1+a)}{(a+1)(1+3a^2)}=frac{a(1-a)}{1-3a^2}=frac{a-a^2}{1-3a^2}$