If the sum of odd numbered terms and the sum of even numbered terms in the expansion of…

If the sum of odd numbered terms and the sum of even numbered terms in the expansion of \((\text{x}+\text{a})^{\text{n}}\) are A and B respectively, then the value of \((\text{x}^{2}-\text{a}^{2})^{\text{n}}\) is:

  1. A2 - B2

  2. A2 + B2

  3. 4AB

  4. None of these.

Solution

Solution:

If A and B denote respectively the sums of odd terms and even terms in the expansion \((\text{x}+\text{a})^{\text{n}}.\)

Then,

\((\text{x}+\text{a})^{\text{n}}=\text{A}+\text{B}\ ...(\text{i})\)

\((\text{x}-\text{a})^{\text{n}}=\text{A}-\text{B}\ ...(\text{ii})\)

Multplying both the equations we get,

\((\text{x}+\text{a})^{\text{n}}(\text{x}-\text{a})^{\text{n}}=\text{A}^{2}-\text{B}^{2}\)

\(\Rightarrow (\text{x}-\text{a})^{\text{n}}=\text{A}^{2}-\text{B}^{2}\)

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