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Exercise 9.1 - Chapter 9 Sequences & Series class 11 ncert solutions Maths - SaraNextGen [2024-2025]


Question 1:

Write the first five terms of the sequences whose nth term is https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5421/chapter%209_html_f556abe.gif

Answer:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5421/chapter%209_html_f556abe.gif

Substituting n = 1, 2, 3, 4, and 5, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5421/chapter%209_html_10c33c35.gif

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 https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5422/chapter%209_html_m4ccefe05.gif

Answer:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5422/chapter%209_html_m4ccefe05.gif

Substituting n = 1, 2, 3, 4, 5, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5422/chapter%209_html_50a3fda2.gif

Therefore, the required terms arehttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5422/chapter%209_html_794f5c97.gif.

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

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5423/chapter%209_html_5a6df541.gif

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 https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5594/Chapter%209_html_15221dac.gif

Answer:

Substituting = 1, 2, 3, 4, 5, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5594/Chapter%209_html_4019a72b.gif

Therefore, the required terms arehttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5594/Chapter%209_html_mfa0ca6d.gif.

Question 5:

Write the first five terms of the sequences whose nth term is https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5595/Chapter%209_html_459c0493.gif

Answer:

Substituting = 1, 2, 3, 4, 5, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5595/Chapter%209_html_m71955e23.gif

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 https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5596/Chapter%209_html_m139cb272.gif

Answer:

Substituting n = 1, 2, 3, 4, 5, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5596/Chapter%209_html_748ef08a.gif

Therefore, the required terms arehttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5596/Chapter%209_html_2c510480.gif

Question 7:

Find the 17th term in the following sequence whose nth term ishttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5597/Chapter%209_html_104e0b82.gif

Answer:

Substituting n = 17, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5597/Chapter%209_html_79c44e87.gif

Substituting n = 24, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5597/Chapter%209_html_589a83d9.gif

Question 8:

Find the 7th term in the following sequence whose nth term ishttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5598/Chapter%209_html_m645a83cc.gif

Answer:

Substituting n = 7, we obtain

https://img-nm.mnimgs.com/img/study_content/editlive_ncert/90/2012_04_09_16_59_00/mathmlequation2664305987458295483.png

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

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5428/chapter%209_html_m304b19e8.gif

Question 9:

Find the 9th term in the following sequence whose nth term ishttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5599/Chapter%209_html_m63c6aa98.gif

Answer:

Substituting n = 9, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5599/Chapter%209_html_m56e4a1d5.gif

Question 10:

Find the 20th term in the following sequence whose nth term is https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5600/Chapter%209_html_m6721ac9.gif

Answer:

Substituting = 20, we obtain

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5600/Chapter%209_html_m4de0ac67.gif

Question 11:

Write the first five terms of the following sequence and obtain the corresponding series:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5431/chapter%209_html_m13058db2.gif

Answer:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5431/chapter%209_html_m13058db2.gif

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5431/chapter%209_html_6d1fc392.gif

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:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5432/chapter%209_html_7c8c8d9.gif

Answer:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5432/chapter%209_html_7c8c8d9.gif

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5432/chapter%209_html_m27af2a86.gif

Hence, the first five terms of the sequence arehttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5432/chapter%209_html_m50f78fa0.gif

The corresponding series ishttps://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5432/chapter%209_html_m2a48d4b2.gif

Question 13:

Write the first five terms of the following sequence and obtain the corresponding series:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5433/chapter%209_html_m36227c66.gif

Answer:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5433/chapter%209_html_m36227c66.gif

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5433/chapter%209_html_5b173a0e.gif

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

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5601/Chapter%209_html_613ee0fc.gif

Find https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5601/Chapter%209_html_4a3d1d91.gif

Answer:

https://img-nm.mnimgs.com/img/study_content/curr/1/11/11/169/5601/Chapter%209_html_m1082c6c0.gif

Also Read : Exercise-9.2-Chapter-9-Sequences-&-Series-class-11-ncert-solutions-Maths

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