Question

An= 2an-1 +5 what is the value of a5

a1 = 1

Answer 1

`a_5=91`

Explanation:

The general term formula is:

`a_n=2a_(n-1)+5`

And given first term is "1",

The general term formula means, to get a term, multiply the previous term by 2 and sum it with "5".

Lets find a_2:

`a_2=2a_(1)+5\\a_2=2(1)+5\\a_2=7`

Now, finding a_3:

`a_3=2a_2+5\\a_3=2(7)+5\\a_3=19`

Now, a_4:

`a_4=2a_3+5\\a_4=2(19)+5\\a_4=43`

Finally, finding a_5:

`a_5=2a_4+5\\a_5=2(43)+5\\a_5=91`

This is the answer.