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CLASS_11_MATHS_SOLUTIONS_NCERT

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Class XI Chapter 4 – Principle of Mathematical Induction Maths<br />

______________________________________________________________________________<br />

1k<br />

2<br />

k k <br />

1.2 2.3 3.4 ..... k. k 1 ....... i<br />

3 <br />

We shall now prove that<br />

Consider<br />

<br />

P k 1<br />

<br />

is true.<br />

<br />

1.2 2.3 3.4 .... k. k 1 k 1 . k 2<br />

<br />

1.2 2.3 3.4 ..... k. k 1 k 1 . k 2<br />

1k<br />

2<br />

k k<br />

k 1k 2 Using<br />

i<br />

3<br />

<br />

k<br />

<br />

k1k 2<br />

1<br />

3<br />

<br />

<br />

<br />

k 1k 2k<br />

3<br />

3<br />

<br />

Thus,<br />

k 1 k <strong>11</strong> k 1<br />

2<br />

<br />

P k 1<br />

<br />

3<br />

is true whenever<br />

Pk<br />

is true.<br />

Hence, by the principle of mathematical induction, statement<br />

numbers i.e., N.<br />

<br />

Pn<br />

is true for all natural<br />

Question 7:<br />

Prove the following by using the principle of mathematical induction for all<br />

n n n<br />

1.3 3.5 5.7 ..... 2n12n1<br />

<br />

3<br />

Solution 7:<br />

Let the given statement be P(n), i.e.,<br />

<br />

2<br />

4 6 1<br />

n n n<br />

Pn :1.3 3.5 5.7 ..... 2n 12n<br />

1<br />

<br />

3<br />

For n = 1, we have<br />

<br />

<br />

<br />

2<br />

1 4.1 6.<strong>11</strong> 4 6 1 9<br />

P 1 :1.3 3 3<br />

3 3 3<br />

Let<br />

Pk be true for some positive integer k, i.e.,<br />

<br />

<br />

<br />

2<br />

4 6 1<br />

<br />

, which is true.<br />

2<br />

k 4k 6k<br />

1<br />

1.3 3.5 5.7 ..... 2k 12k 1 <br />

....... i<br />

3<br />

<br />

<br />

n<br />

N:

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