Question

The (n-1)th term of an ap is given by 7 12 17 22 is

Answer 1

Step-by-step explanation:

the given ap is 7,12,17,22.......;first term(a) is 7,commmon difference (d) is 12-7=5.

nth term is n(2a+(n-1)d)÷2

for n-1th term

n-1(2a+(n-1-1) d) ÷2

=n-1(2a+(n-2)d) ÷2

by substituting values of a and d

n-1(2(7)+(n-2) 5)÷2

n-1(14+5n-10)÷2

n-1(4-5n)÷2

4n-5n^2-4+5n÷2

(9n-5n^2+5n)÷2 is your answer. I hope you are satisfied by my answer.

Answer 2

The information given is incomplete, because the total no. of terms should be given, and which term you want to find should be given like 16th, 20th etc. then it can be calculated.

For finding nth term

$an \: = a + (n - 1) \: d$

where

an = nth term (you want to find)

a = first term of A.P (It is 7 in your A.P)

n = total no. of terms.

d = difference of terms (It is 5 in the given A.P)