Question

If the sixth term of a sequence is 128 and the common ratio is 2, then what is the first term?

Answer 1

general equation for geometric sequence: \[a _{n}=a _{1}*r ^{n-1}\]
since we know the 6th term, we can plug it into our general equation
\[(128)=a_{1}*(2)^{(6)-1}\]
\[128=a _{1}*32\]
solve for a1