Question 928433
{{{a[n]=-21+9n}}}
{{{S[n]=(n/2)(a[1]+a[n])}}}
{{{363=(n/2)(-12-21+9n)}}}
{{{726=n(9n-33)}}}
{{{9n^2-33n=726}}}
{{{3n^2-11n-242=0}}}
{{{(n-11)(3n+22)=0}}}
Only the positive solution makes sense here.
{{{n-11=0}}}
{{{n=11}}}{{{terms}}}