Question #16a2c

1 Answer
Jan 6, 2018

3rd term is 20

Explanation:

This is called a geometric sequence, these have the genral nth term foruma of:

#a_n = a * r^(n-1) #

Where #a - "first term " n = 1 #

#r = "common ration" = a_2 / a_1 = a_m / a_(m-1) #

Hence the first term of this is #a = 5 #

and the ratio is #10/5 = 2 #

So the nth term of this sequance is #5 * 2^(n-1) #

Applying this formula : #a_3 = 5 * 2^2 = color(red)(20 #

or just looking at the sequence, #color(red)(20) # is the 3rd