Answer
See answers below
Work Step by Step
a) $2,4,8,16,...$
The starting value is 2. The common ratio r is $\frac{4}{2}=2$
The recursive formula is $a_1=2; a_n=a_{n-1}.2$
The explicit formula is $a_n=2.2^{n-1}$
a) $40,20,10,5,...$
The starting value is 40. The common ratio r is $\frac{20}{40}=\frac{1}{2}$
The recursive formula is $a_1=40; a_n=a_{n-1}.\frac{1}{2}$
The explicit formula is $a_n=40.\frac{1}{2}^{n-1}$
