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Write the middle term or terms in the ex...

Write the middle term or terms in the expansion of
(i) `(x^(2) - (1)/(x) )^6`

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To find the middle term(s) in the expansion of \((x^2 - \frac{1}{x})^6\), we will follow these steps: ### Step 1: Identify the values of \(n\) In the expression \((x^2 - \frac{1}{x})^6\), we have \(n = 6\). **Hint:** The exponent in the binomial expression is key to determining the number of terms in the expansion. ### Step 2: Determine the number of terms The number of terms in the expansion of \((x + y)^n\) is \(n + 1\). Therefore, for \(n = 6\), the number of terms is \(6 + 1 = 7\). **Hint:** Remember that for any binomial expansion \((a + b)^n\), the number of terms is \(n + 1\). ### Step 3: Identify the middle term Since \(n = 6\) is even, the middle term will be the \(\frac{n}{2} + 1\)th term, which is the \(4\)th term. **Hint:** For even \(n\), the middle term is found using the formula \(\frac{n}{2} + 1\). ### Step 4: Write the general term The general term \(T_{r+1}\) in the expansion of \((x^2 - \frac{1}{x})^n\) is given by: \[ T_{r+1} = \binom{n}{r} (x^2)^{n-r} \left(-\frac{1}{x}\right)^r \] For our case: \[ T_{r+1} = \binom{6}{r} (x^2)^{6-r} \left(-\frac{1}{x}\right)^r \] **Hint:** The general term formula is crucial for finding specific terms in the expansion. ### Step 5: Substitute \(r = 3\) for the 4th term To find the 4th term, substitute \(r = 3\): \[ T_{4} = \binom{6}{3} (x^2)^{6-3} \left(-\frac{1}{x}\right)^3 \] Calculating this gives: \[ T_{4} = \binom{6}{3} (x^2)^{3} \left(-\frac{1}{x}\right)^3 = \binom{6}{3} x^6 \cdot \left(-\frac{1}{x^3}\right) \] **Hint:** Make sure to carefully apply the binomial coefficient and simplify the powers of \(x\). ### Step 6: Simplify the expression Now, simplify: \[ T_{4} = \binom{6}{3} x^{6 - 3} \cdot (-1) = \binom{6}{3} x^{3} \cdot (-1) \] Calculating \(\binom{6}{3}\): \[ \binom{6}{3} = \frac{6!}{3!3!} = 20 \] Thus, we have: \[ T_{4} = 20 \cdot (-1) \cdot x^{3} = -20x^{3} \] ### Conclusion The middle term in the expansion of \((x^2 - \frac{1}{x})^6\) is: \[ \boxed{-20x^{3}} \]
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