Answer:
a(n) = 10n-1 (the second one)
Step-by-step explanation:
we use formula
a(n) = a +(n-1)d (a= the first number in the, n=the times we need, d= difference)
a=9
d=9-19=10
a(n) = 9 +(n-1)10
a(n) = 9 +10n-10
a(n) = 10n-1 (the second one)
I hope it will help
