Verified Answer :

A recursive rule for a geometric sequence is a1=3;an=1/2(an−1) 
explicit rule 
an = (3)(1/2
)^n−1

Answer:The explicit rule for this sequence:

\(a_n=a_1(r)^{n-1}=3(\frac{1}{2})^{n-1}\)

Step-by-step explanation:

\(a_1=3\)

\(a_n=\frac{1}{2}a_{n-1}\)

Where \(a_n\) = n'th term in a sequence

\(a_2=\frac{1}{2}a_{(2-1)}=\frac{1}{2}a_1=\frac{1}{2}\times 3=\frac{3}{2}\)

The value 'r' is geometric mean is given as:

r = common ratio

\(r=\frac{a_2}{a_1}=\frac{\frac{3}{2}}{3}=\frac{1}{2}\)

The explicit rule for this sequence:

\(a_n=a_1(r)^{n-1}=3(\frac{1}{2})^{n-1}\)