Question 369787
in an arithmetic sequence, means that each term changes by a constant amount, delta
--
The nth term is defined as {{{a[n]=a[1]+(n-1)*delta}}}
from this formula {{{delta=(a[n]-a[1])/(n-1)}}}
==
So if {{{a[1]=3}}} and {{{a[52]=142}}} then {{{delta=(142-3)/(52-1)=139/51}}}
--
{{{a[89]=3+(89-1)*139/51=3+88*139/51}}}