NCERT Solutions
Class 11 - Mathematics
Chapter 7: BINOMIALTHEOREM

Complete NCERT Solutions for problems given in BINOMIALTHEOREM chapter in Class 11 Mathematics.

EXERCISE 7.1

Question. 1

Expand \((1 - 2x)^5\).

Answer:

\(1 - 10x + 40x^2 - 80x^3 + 80x^4 - 32x^5\)

Question. 2

Expand \(\left( \dfrac{2}{x} - \dfrac{x}{2} \right)^5\).

Answer:

\(\dfrac{32}{x^5} - \dfrac{40}{x^3} + \dfrac{20}{x} - 5x + \dfrac{5}{8}x^3 - \dfrac{x^5}{32}\)

Question. 3

Expand \((2x - 3)^6\).

Answer:

\(64x^6 - 576x^5 + 2160x^4 - 4320x^3 + 4860x^2 - 2916x + 729\)

Question. 4

Expand \(\left( \dfrac{x}{3} + \dfrac{1}{x} \right)^5\).

Answer:

\(\dfrac{x^5}{243} + \dfrac{5x^3}{81} + \dfrac{10x}{27} + \dfrac{10}{9x} + \dfrac{5}{3x^3} + \dfrac{1}{x^5}\)

Question. 5

Expand \(\left( x + \dfrac{1}{x} \right)^6\).

Answer:

\(x^6 + 6x^4 + 15x^2 + 20 + \dfrac{15}{x^2} + \dfrac{6}{x^4} + \dfrac{1}{x^6}\)

Question. 6

Using Binomial Theorem, evaluate \(96^3\).

Answer:

884736

Question. 7

Using Binomial Theorem, evaluate \(102^5\).

Answer:

11040808032

Question. 8

Using Binomial Theorem, evaluate \(101^4\).

Answer:

104060401

Question. 9

Using Binomial Theorem, evaluate \(99^5\).

Answer:

9509900499

Question. 10

Using Binomial Theorem, indicate which number is larger: \((1.1)^{10000}\) or 1000.

Answer:

\((1.1)^{10000} > 1000\)

Question. 11

Find \((a + b)^4 - (a - b)^4\). Hence, evaluate \((\sqrt{3} + \sqrt{2})^4 - (\sqrt{3} - \sqrt{2})^4\).

Answer:

\(8(a^3b + ab^3);\ 40\sqrt{6}\)

Question. 12

Find \((x + 1)^6 + (x - 1)^6\). Hence evaluate \((\sqrt{2} + 1)^6 + (\sqrt{2} - 1)^6\).

Answer:

\(2(x^6 + 15x^4 + 15x^2 + 1),\ 198\)

Question. 13

Show that \(9^{n+1} - 8n - 9\) is divisible by 64 whenever \(n\) is a positive integer.

Answer:

40\sqrt{6}

Question. 14

Prove that \(\sum_{r=0}^{n} 3^r \binom{n}{r} = 4^n\).

Answer:

Answer not provided in the screenshot.

Miscellaneous Exercise on Chapter 7

Question. 1

If \(a\) and \(b\) are distinct integers, prove that \(a - b\) is a factor of \(a^n - b^n\), whenever \(n\) is a positive integer.

Answer:

Use expansion: \(a^n = (a - b + b)^n\). Hence \(a^n - b^n\) is divisible by \(a - b\).

Question. 2

Evaluate \((\sqrt{3} + \sqrt{2})^6 - (\sqrt{3} - \sqrt{2})^6\).

Answer:

396\(\sqrt{6}\)

Question. 3

Find the value of \((a^2 + \sqrt{a^2 - 1})^4 + (a^2 - \sqrt{a^2 - 1})^4\).

Answer:

\(2a^8 + 12a^6 - 10a^4 - 4a^2 + 2\)

Question. 4

Find an approximation of \((0.99)^5\) using the first three terms of its expansion.

Answer:

0.9510

Question. 5

Expand using Binomial Theorem: \(\left(1 + \dfrac{x}{2} - \dfrac{2}{x}\right)^4\), \(x \neq 0\).

Answer:

\(\dfrac{16}{x} + \dfrac{8}{x^2} - \dfrac{32}{x^3} + \dfrac{16}{x^4} - 4x + \dfrac{x^2}{2} + \dfrac{x^3}{2} + \dfrac{x^4}{16} - 5\)

Question. 6

Find the expansion of \((3x^2 - 2ax + 3a^2)^3\) using binomial theorem.

Answer:

27x^6 - 54ax^5 + 117a^2x^4 - 116a^3x^3 + 117a^4x^2 - 54a^5x + 27a^6

NCERT Solutions Class 11 – Mathematics – Chapter 7: BINOMIALTHEOREM | Detailed Answers