/sci/ - Science & Math

>>11325627
BUMP PLEASE HELP

I don't understand how the n^3 term simplifies to n^3/3, I continually keep getting 2n^3/3 and see no other way.

the (n+1)^5 expands into a polynomial containing 2n^3, the (10*(n^3/2))/5 simplifies to -n^3, and the n(n+1)(n+2) expression contains -n^3/3 after simplification. So 2n^3 - n^3 -n^3/3 = 2n^3/3, but obviously I'm wrong.