NCERT Class 11-Math's: Chapter –8 Binomial Theorem Part 7

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Question 10:

If the coefficient of second, third and fourth terms in the expansion of are in A.P. Show that.

Answer:

Given expression are in A.P., show that

Coefficient of second term

Coefficient of third term

and Coefficient of fourth term

As the given condition, and are in A.P.

Hence proved.

Question 11:

Find the coefficient of in the expansion of .

Answer:

Long Answer Type

Question 12:

If is a real number and if the middle term in the expansion of is , find .

Answer:

Given expression is

Number of terms

Middle term

Now

Hence, the required value of

Question 13:

Show that the middle term in the expansion of is

Answer:

Given expression is

Number of terms (odd)

Middle term

General Term

Hence, the middle term