Question

si a1= 5 y el 18 termino es -80 halla la razon

Answer 1

an = -80
a1 = 5
n   = 18
r    = 

an = a1+(n-1)r

-80 = 5+(18-1)r
-80-5 = (17)r
-85 = (17)r
-85/17 = r
-5 = r

La razón es -5