Question

Given the terms a1=5 and a4=14 of an arithmetic sequence, what is a20?

Answer 1

@jim_thompson5910

Answer 2

a[4] - a[1] = 14 - 5 = 9


So d = 9/3 = 3. This means we're adding 3 to each term to get the next term

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a[n] = a[1] + (n-1)*d


a[n] = 5 + (n-1)*3


a[n] = 5 + 3n-3


a[n] = 3n + 2


So the nth term is 3n+2


This means that the 20th term is


3n+2


3*20+2


60+2


62


So the 20th term is 62

Answer 3

So a20 = 62

Answer 4

Thank you sooo much! =)

Answer 5

you're welcome again:)