NCERT Solutions for Class 11 Maths Chapter 9 – Sequences and Series Ex 9.1
Page No 180:
Question 1:
Write the first five terms of the sequences whose nth term is 
Answer:
Substituting n = 1, 2, 3, 4, and 5, we obtain
Therefore, the required terms are 3, 8, 15, 24, and 35.
Question 2:
Write the first five terms of the sequences whose nth term is 
Answer:
Substituting n = 1, 2, 3, 4, 5, we obtain
Therefore, the required terms are
.
.Question 3:
Write the first five terms of the sequences whose nth term is an = 2n
Answer:
an = 2n
Substituting n = 1, 2, 3, 4, 5, we obtain
Therefore, the required terms are 2, 4, 8, 16, and 32.
Question 4:
Write the first five terms of the sequences whose nth term is 
Answer:
Substituting n = 1, 2, 3, 4, 5, we obtain
Therefore, the required terms are
.
.Question 5:
Write the first five terms of the sequences whose nth term is 
Answer:
Substituting n = 1, 2, 3, 4, 5, we obtain
Therefore, the required terms are 25, –125, 625, –3125, and 15625.
Question 6:
Write the first five terms of the sequences whose nth term is 
Answer:
Substituting n = 1, 2, 3, 4, 5, we obtain
Therefore, the required terms are
Question 7:
Find the 17th term in the following sequence whose nth term is
Answer:
Substituting n = 17, we obtain
Substituting n = 24, we obtain
Question 8:
Find the 7th term in the following sequence whose nth term is
Answer:
Substituting n = 7, we obtain
Question 8:
Find the indicated terms in each of the sequences in Exercises 7 to 10 whose nth terms are :
an = n22n ; a7
Answer:
Here,
an=n22n.
Substituting n = 7, we obtain
Question 9:
Find the 9th term in the following sequence whose nth term is
Answer:
Substituting n = 9, we obtain
Question 10:
Find the 20th term in the following sequence whose nth term is 
Answer:
Substituting n = 20, we obtain
Page No 181:
Question 11:
Write the first five terms of the following sequence and obtain the corresponding series:
Answer:
Hence, the first five terms of the sequence are 3, 11, 35, 107, and 323.
The corresponding series is 3 + 11 + 35 + 107 + 323 + …
Question 12:
Write the first five terms of the following sequence and obtain the corresponding series:
Answer:
Hence, the first five terms of the sequence are
The corresponding series is
Question 13:
Write the first five terms of the following sequence and obtain the corresponding series:
Answer:
Hence, the first five terms of the sequence are 2, 2, 1, 0, and –1.
The corresponding series is 2 + 2 + 1 + 0 + (–1) + …
Question 14:
The Fibonacci sequence is defined by
Find 
Answer:
