Question

Find the 15th term from the last term (towards the first term) of the AP:3,7,11....123

Answer 1

Answer:

3,7,11,....,123.

a15=?

a=3, d=7-3=4.

l=a+(n-1)d.

123=3+(n-1)(4)

123=3+4n-4.

123=-1+4n.

123+1=4n.

124=4n.

124/4=n.

31=n.

an=a+(n-1)d.

a15=3+(31-1)(4).

a15=3+(30)(4).

a15=3+120.

a15=123.

I think this is your answer.