Question 758153
Sequence: {{{a}}}, {{{a*3}}}, {{{a*3*3}}}, {{{a*3*3*3}}},...


{{{t[3]=-81=a*3*3}}}
{{{(-1)3*3*3*3=a*3*3}}}
{{{highlight(a=-9)}}}


Now you can find the first four terms and find their sum.


-9, -9*3, -9*3*3, -9*3*3*3
sum: {{{-9-9*3-9*9-9*27}}}
={{{-9(1+3+9+27)}}} and there is a formula if you want it, but even without,
={{{-9(40)}}}
={{{-360}}}