Question 1126167


For arithmetic sequences, we use the formula 

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

where {{{a[n] }}} is the term we are trying to find, {{{a[1] }}}is the first term, and {{{d}}} is the difference between consecutive terms, and {{{n}}} is the number of the term. 


If the 100th term of an arithmetic sequence is {{{a[100]=213}}}, {{{n=100}}}, and its common difference is {{{d=2}}},  then its first term

{{{213=a[1]+(100-1)2}}} 
{{{213=a[1]+(99)2}}} 
{{{213=a[1]+198}}} 
{{{a[1]=213-198}}} 
{{{a[1]=15}}} 


{{{a[2]=a[1]+(2-1)d}}}
{{{a[2]=15+(1)2}}}
{{{a[2]=17}}}


{{{a[3]= 19}}}