Solution of Chapter 8. Binomial Theorem (NCERT - Maths Book)

Chapter Exercises

Exercise 8.1

1

Expand each of the expressions in Exercises 1 to 5.

(1 – 2x)5

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2

Expand each of the expressions in Exercises 1 to 5.

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3

Expand each of the expressions in Exercises 1 to 5.

(2x – 3)6

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4

Expand each of the expressions in Exercises 1 to 5.

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5

Expand each of the expressions in Exercises 1 to 5.

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6

Using binomial theorem, evaluate each of the following:

(96)3

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7

Using binomial theorem, evaluate each of the following:

(102)5

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8

Using binomial theorem, evaluate each of the following:

(101)4

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9

Using binomial theorem, evaluate each of the following:

(99)5

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10

Using Binomial Theorem, indicate which number is larger (1.1)10000 or 1000.

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11

Find (a + b)4 – (a – b)4. Hence, evaluate

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12

Find (x + 1)6 + (x – 1)6. Hence or otherwise evaluate .

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13

Show that 9n+1 – 8n – 9 is divisible by 64, whenever n is a positive integer.

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14

Prove that

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Exercise 8.2

1

Find the coefficient of

x5 in (x + 3)8

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2

Find the coefficient of

a5b7 in (a – 2b)12 .

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3

Write the general term in the expansion of

(x2 – y)6

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4

Write the general term in the expansion of

(x2 – yx)12, x ≠ 0.

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5

Find the 4th term in the expansion of (x – 2y)12.

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6

Find the 13th term in the expansion of

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7

Find the middle terms in the expansions of

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8

Find the middle terms in the expansions of

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9

In the expansion of (1 + a)m+n, prove that coefficients of am and an are equal.

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10

The coefficients of the (r – 1)th, rth and (r + 1)th terms in the expansion of (x + 1)n are in the ratio 1 : 3 : 5. Find n and r.

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11

Prove that the coefficient of xn in the expansion of (1 + x)2n is twice the coefficient of xn in the expansion of (1 + x)2n – 1.

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12

Find a positive value of m for which the coefficient of x2 in the expansion (1 + x)m is 6.

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Miscellaneous Exercise

1

Find a, b and n in the expansion of (a + b)n if the first three terms of the expansion are 729, 7290 and 30375, respectively.

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2

Find a if the coefficients of x2 and x3 in the expansion of (3 + ax)9 are equal.

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3

Find the coefficient of x5 in the product (1 + 2x)6 (1 – x)7 using binomial theorem.

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4

If a and b are distinct integers, prove that a – b is a factor of an – bn, whenever n is a positive integer. [Hint write an = (a – b + b)n and expand]

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5

Evaluate

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6

Find the value of

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7

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

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8

Find n, if the ratio of the fifth term from the beginning to the fifth term from the end in the expansion of is √6 : 1

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9

Expand using Binomial Theorem

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10

Find the expansion of (3x2 – 2ax + 3a2)3 using binomial theorem.

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