The equation is: [i(i+1)=n(n+1)(n+2)/3] whereas i=1
so the beginning process would be 2+6+12+20...+n(n+1)=n(n+1)(n+2)/3
after the equation is proven for n=1 [(1(1+1)=1(1+1)(1+2)/3] then we must prove for n=n+1
thats where i begin to stop understanding.
So...