Question

1 1 1 1
3. Is the sequence 7' 5'8' 11'
· an A.P.? If it is an
A.P., then find its common difference.​

Answer 1

Step-by-step explanation:

d= 5-7= -2

d= 8-5= 3

d= 11-8 =3

- done

Answer 2

Step-by-step explanation:

We have,

ANSWER

We have,

a =a= First term = -7=−7 and, d =d= Common difference = 5=5

a_{18} = a + (18 - 1)da

18

=a+(18−1)d [\because a_n = a + (n - 1)d][∵a

n

=a+(n−1)d]

\Longrightarrow a_{18} = a + 17d = -7 + 17 \times 5 = 78⟹a

18

=a+17d=−7+17×5=78

and the general term a_n = a + (n - 1) \times 5 = -7 + (n - 1) \times 5a

n

=a+(n−1)×5=−7+(n−1)×5

\Longrightarrow a_n = -7 + 5n - 5 = 5n - 12⟹a

n

=−7+5n−5=5n−12