a)
1+6+6^2+...+6^2015=x (inmultim cu 6)
6+6^2+6^3+...+6^2015+6^2016=6x (adunam 1)
(1+6+6^2+6^3+...+6^2015)+6^2016=6x +1
x+6^2016=6x+1
5x=6^2016 -1
x=(6^2016 -1)/5
5x+1=5*[(6^2016 -1)/5]+1=(6^2016 -1)+1=6^2016
"V"=radical
V(5x+1)=V(6^2016)=6^1008
b)
V[(-2)^4 x(-3)^4 x5^2]-V[(-2)^4 x(+3)^2 x(-5)^2]=
=2^2 x3^2 x5 - 2^2 x3 x5=4x9x5-4x3x5=4x5(9-3)=4x5x6=120