Question

прошу помочь с алгеброй

Answer 1

$( frac{3a+1}{a-1} -a)* frac{6}{a+1} = frac{3a+1+a(a-1)}{a-1} * frac{6}{a+1} = frac{(3a+1+ a^{2}-a )*6}{(a-1)(a+1)} = frac{6*( a^{2} +2a+1)}{(a-1)(a+1)} = \ \ = frac{6 (a+1)^{2} }{(a-1)(a+1)} = frac{6(a+1)}{a-1}$