# 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