Question

Find the fifth term of the arithmetic sequence in which

t1 = 3 and tn = tn-1 + 4.

A) 5
B) 7
C) 19
D) 23

Answer 1

We have given
`t_(1)=3` and
`t_(n) = t_(n-1) + 4`. Fifth term is
`t_(5)= t_(4)+4`. It means we need to find
`t_(4)` and in order to find the latter, we have to find
`t_(4)= t_(3)+4`,
`t_(3)= t_(2)+4` and
`t_(2)= t_(1)+4` . Since we know the value of
`t_(1)`, beginning from the last equation we can find the value of
`t_(5)`. We can write that
`t_(2)= t_(1)+4=3+4=7`,
`t_(3)= t_(2)+4=7+4=11` and
`t_(4)= t_(3)+4=11+4=15`. Since
`t_(5)= t_(4)+4`, then
`t_(5)= 15+4=19`