Question 388655
{{{a[9]=a[1]+(9-1)*d}}}
1.{{{85=a[1]+8d}}}
.
.
2.{{{295=a[1]+30d}}}
Subtract eq. 1 from eq. 2,
{{{a[1]+29d-a[1]-8d=295-85}}}
{{{21d=210}}}
{{{d=10}}}
Then use either equation to solve for {{{a[1]}}}.
{{{a[1]+80=85}}}
{{{a[1]=5}}}
So then,
{{{a[n]=a[1]+(n-1)d}}}
{{{a[n]=5+(n-1)(10)}}}
{{{a[n]=5+10n-10}}}
{{{highlight(a[n]=10n-5)}}}