Question 1012112
If f(n) is a function that gives you the sum of the first n terms, the nth term is given by subtracting away the previous terms. Since terms are integers apart (1,2,3), we can extract the nth term by taking the sum to n, and subtracting away the sum of n-1. Thus, n=f(n)-f(n-1).
*[invoke explain_simplification "2n^2+3n+4-2(n-1)^2+3(n-1)+4" ]