Answer:
a[1] = 80; a[n] = -a[n-1]/4
Step-by-step explanation:
The given sequence has a first term of 80 and a common ratio of -20/80 = -1/4. That is, each term is -1/4 times the previous one. The recursive formula is ...
[tex]A_1=80\\A_{n}=-\dfrac{1}{4}\times A_{n-1}[/tex]
