Question

The explicit formula

Answer 1

Answer:

Below.

Step-by-step explanation:

{ a1 = 0.5

{ an = an-1*(-0.2)

The first 4 terms are:

= 0.5, -0.1, 0.02, -0.004

Answer 2

Answer:

Step-by-step explanation:

$a_n=\dfrac{1}{2} *(\dfrac{-1}{5} )^{n-1}\\\\a_{n+1}=\dfrac{1}{2} *(\dfrac{-1}{5} )^{n}\\\\\\\\\dfrac{a_{n+1}}{a_n} =\dfrac{\dfrac{1}{2} *(\dfrac{-1}{5} )^{n}}{\dfrac{1}{2} *(\dfrac{-1}{5} )^{n-1}} =\dfrac{-1}{5} \\a_1=\dfrac{1}{2} *(\dfrac{-1}{5} )^{0}=\dfrac{1}{2} \\\\\\\boxed{a_1=\dfrac{1}{2}}\\\boxed{a_{n } =-\dfrac{1}{5} *a_{n-1} }\\\\\\a_1=\dfrac{1}{2}\\\\a_2=\dfrac{-1}{10}\\\\a_3=\dfrac{1}{50}\\\\a_4=\dfrac{-1}{250}$