Can someone explain/ write out step by step how the professor got from the first equation to the second?

2 8n,n, = + 2 V = lnV) n 15n, 'n nV = 120n, + 70n2 + (n, +n2)2 .. (ni +n2) (n+n2){(15* 2n,nz)-(15n?n,)* 2(n, + n) - 120 + (n+n) ,* (n + n,)?(8n,)(8n,n22) * 2(n, + n) (n + n2)" - 4 P,1,n2 2 - + 4