Question

Tell whether each sequence is arithmetic or geometric and determine the 11th term. (a) 3, 10, 17, 24, ... arithmetic or geometric? 11th term: (b) 4, 12, 36, 108, ... arithmetic or geometric? 11th term: (c) -20, -24, -28, -32, ... arithmetic or geometric? 11th term:

Answer 1

Explanation:

(a) 3, 10, 17, 24, ...

d=10-3=17-10=7 then it is arithmetic sequence

a(n) = a +(n-1)d

a(11) = 3 +(11-1)7

=73

(b) 4, 12, 36, 108,

r=12/4=36/12=108/36=3

So it is geometric

By using this equation:

and we have a(1)=4 , r=3

a(11)=4*(3)^(11-1)

=236196

(c) -20, -24, -28, -32, ...

d=-24+20=-28+24=-4 then it is arithmetic sequence

a(11) = -20 +(11-1)-4

=-60

hope this helps