Question 1070095
{{{a[n]=a[1]+(n-1)d}}}
{{{a[12]=a[1]+(12-1)d=38}}}
{{{a[1]+11d=38}}}
.
.
{{{a[1]+84d=257}}}
Subtracting the first equation from this equation,
{{{a[1]+84d-a[1]-11d=257-38}}}
{{{73d=219}}}
{{{d=3}}}
Then,
{{{a[1]+11(3)=38}}}
{{{a[1]+33=38}}}
{{{a[1]=5}}}
So then,
{{{a[1]+(k-1)d=395}}}
Find k.
{{{5+(k-1)3=395}}}
{{{(k-1)3=390}}}
{{{k-1=130}}}
{{{k=131}}}
131 terms