Question 943026
On this site, { { { a[n] = a[1] + (n-1)d } } } gives {{{a[n] = a[1] + (n-1)d}}} (remove spaces)


In TeX/LaTeX, (using * [tex \large a_n = a_1 + (n-1)d ]   gives *[tex \large a_n = a_1 + (n-1)d] (remove spaces)


You can solve for n but it will be in terms of *[tex \large a_n].


*[tex \large (n-1)d = a_n - a_1]


*[tex \large n-1 = \frac{a_n - a_1}{d}]


*[tex \large n = \frac{a_n - a_1}{d} + 1]