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(p + 2)th term from the end in the binom...

(p + 2)th term from the end in the binomial expansion of `(x^(2)-2/(x^(2)))^(2n+1)` is

A

`""^(2n+1)C_(2n-p)(-2)^(2n-p)x^(2p+1-2n)`

B

`""^(2n+1)C_(2n-p)(-2)^(2n-p)x^(2n-2p)`

C

`""^(2n+1)C_(2n-p)(-2)^(2n-p)x^(2n-2p+1)`

D

`""^(2n+1)C_(2n-p)(-2)^(2n-p)x^(2p-1+2n)`

Text Solution

AI Generated Solution

The correct Answer is:
To find the \((p + 2)\)th term from the end in the binomial expansion of \((x^2 - \frac{2}{x^2})^{2n + 1}\), we will follow these steps: ### Step 1: Understand the Binomial Expansion The general term in the binomial expansion of \((a + b)^n\) is given by: \[ T_r = \binom{n}{r} a^{n-r} b^r \] In our case, \(a = x^2\), \(b = -\frac{2}{x^2}\), and \(n = 2n + 1\). ### Step 2: Identify the Total Number of Terms In the expansion of \((x^2 - \frac{2}{x^2})^{2n + 1}\), the total number of terms is \(n + 1 = (2n + 1) + 1 = 2n + 2\). ### Step 3: Find the Corresponding Term from the Beginning The \((p + 2)\)th term from the end corresponds to the \((2n + 2 - (p + 2))\)th term from the beginning, which simplifies to: \[ (2n + 2 - p - 2) = (2n - p + 1) \] Thus, we need to find the \((2n - p + 1)\)th term from the beginning. ### Step 4: Substitute into the General Term Formula Using the general term formula: \[ T_{r} = \binom{n}{r} a^{n-r} b^r \] For our case: - \(n = 2n + 1\) - \(r = 2n - p\) Thus, the term we need is: \[ T_{2n - p + 1} = \binom{2n + 1}{2n - p} (x^2)^{(2n + 1) - (2n - p)} \left(-\frac{2}{x^2}\right)^{2n - p} \] ### Step 5: Simplify the Expression Calculating the powers: - The exponent of \(x^2\) becomes: \[ (2n + 1) - (2n - p) = p + 1 \] - The exponent of \(-\frac{2}{x^2}\) becomes: \[ 2n - p \] Thus, we have: \[ T_{2n - p + 1} = \binom{2n + 1}{2n - p} (x^2)^{p + 1} \left(-\frac{2}{x^2}\right)^{2n - p} \] ### Step 6: Combine the Terms Now, we can combine the terms: \[ T_{2n - p + 1} = \binom{2n + 1}{2n - p} (x^{2(p + 1)}) \left(-2\right)^{2n - p} \left(\frac{1}{x^{2(2n - p)}}\right) \] This simplifies to: \[ = \binom{2n + 1}{2n - p} (-2)^{2n - p} x^{2(p + 1) - 2(2n - p)} \] \[ = \binom{2n + 1}{2n - p} (-2)^{2n - p} x^{4p - 4n + 2} \] ### Final Answer Thus, the \((p + 2)\)th term from the end in the binomial expansion of \((x^2 - \frac{2}{x^2})^{2n + 1}\) is: \[ \binom{2n + 1}{2n - p} (-2)^{2n - p} x^{4p - 4n + 2} \]
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