Ответ:

3m-3=9

Объяснение:

2) ...= (m²-1)*(m²+1)*3(m+1) / [(m+1)² * (m²+1)] =

= (m²-1)*3(m+1) / (m+1)² =

= (m-1)*(m+1)*3(m+1) / (m+1)² =

= (m-1) *3 = 3m-3 = [при m=4] =

= 3*4-3=9