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Chapter 8 Binomial Theorem Ex 8.1 Solutions

Question - 11 : -

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

Answer - 11 : -

Using Binomial Theorem, theexpressions, (a + b)4 and (a – b)4,can be expanded as

Question - 12 : -

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

Answer - 12 : -

Using Binomial Theorem, theexpressions, (x + 1)6 and (x – 1)6,can be expanded as

By putting , we obtain

Question - 13 : -

Show that is divisible by 64,whenever n is a positive integer.

Answer - 13 : -

In order to show that  is divisible by 64, it has to be proved that,
 , where k is some natural number
By Binomial Theorem,
 
For a = 8 and m = n + 1, we obtain

Thus, is divisible by 64,whenever n is a positive integer.

Question - 14 : - Prove that .

Answer - 14 : -

By Binomial Theorem,

By putting b = 3and a = 1 in the above equation, we obtain

Hence, proved.

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