[krystar]

continuing where i left off 2*(1+2+...+n) ?=? [n+1]*n

1+2+...+n = n*(n+1)/2 by Carl Gauss

2*n*(n+1)/2 ?=? [n+1]*n
{cancel out 2}
n*(n+1) ?=? [n+1]*n

YES! finished it hehe