Question 1178663


The recursive formula

{{{a[n]=a[1]+d(n-1)}}}

{{{1}}} |{{{3}}}
{{{3}}}|{{{ 8}}}
{{{7}}}|{{{ 18}}}


{{{a[1]=3}}}
{{{8=3+d(3-1)}}}
{{{8-3=2d}}}
{{{2d=5}}}
{{{d=5/2}}}
or
{{{d=2.5}}}

{{{a[n]=3+2.5(n-1)}}}

check  {{{a[7]}}}

{{{a[7] = 3 + 2.5 (7 - 1)=18}}}->true

so, we need 

{{{a[2]=3+2.5(2-1)}}}
{{{a[2]=5.5}}}

{{{a[4]=3+2.5(4-1)}}}
{{{a[4]=10.5}}}

{{{a[5]=3+2.5(5-1)}}}
{{{a[5]=13}}}

{{{a[6]=3+2.5(6-1)}}}
{{{a[6]=15.5}}}


your sequence is:

{{{3}}},{{{5.5}}} ,{{{8}}}, {{{10.5}}},{{{13}}} , {{{15.5}}},{{{18}}}