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Find the 6^(th) term from the end in the...

Find the `6^(th)` term from the end in the expansion of `(2x-(1)/(x^(2)))^(10)` .

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To find the 6th term from the end in the expansion of \( (2x - \frac{1}{x^2})^{10} \), we can follow these steps: ### Step 1: Identify the parameters In the expression \( (2x - \frac{1}{x^2})^{10} \): - \( n = 10 \) (the exponent) - We need to find the 6th term from the end, which corresponds to the \( (n - r + 1) \)-th term from the beginning, where \( r = 6 \). ### Step 2: Calculate the term number from the beginning The term number from the beginning can be calculated as: \[ n - r + 1 = 10 - 6 + 1 = 5 \] So, we need to find the 5th term in the expansion. ### Step 3: Use the binomial theorem The general term \( T_{r+1} \) in the binomial expansion is given by: \[ T_{r+1} = \binom{n}{r} (a)^{n-r} (b)^{r} \] where \( a = 2x \) and \( b = -\frac{1}{x^2} \). For the 5th term, we have: - \( r = 4 \) (since we are looking for the 5th term, \( r \) is one less than the term number) ### Step 4: Substitute values into the formula Now we substitute \( n = 10 \), \( r = 4 \), \( a = 2x \), and \( b = -\frac{1}{x^2} \): \[ T_5 = \binom{10}{4} (2x)^{10-4} \left(-\frac{1}{x^2}\right)^{4} \] ### Step 5: Calculate the binomial coefficient Calculate \( \binom{10}{4} \): \[ \binom{10}{4} = \frac{10!}{4!(10-4)!} = \frac{10 \times 9 \times 8 \times 7}{4 \times 3 \times 2 \times 1} = 210 \] ### Step 6: Calculate the powers Now calculate \( (2x)^6 \) and \( \left(-\frac{1}{x^2}\right)^4 \): \[ (2x)^6 = 2^6 x^6 = 64x^6 \] \[ \left(-\frac{1}{x^2}\right)^4 = \frac{1}{x^8} \] ### Step 7: Combine the results Now substitute back into the term: \[ T_5 = 210 \cdot 64x^6 \cdot \frac{1}{x^8} \] \[ T_5 = 210 \cdot 64 \cdot x^{6-8} = 210 \cdot 64 \cdot x^{-2} \] ### Step 8: Calculate the final coefficient Calculate \( 210 \cdot 64 \): \[ 210 \cdot 64 = 13440 \] ### Final Result Thus, the 5th term (which is the 6th term from the end) is: \[ T_5 = 13440 x^{-2} \] ### Conclusion The required 6th term from the end in the expansion of \( (2x - \frac{1}{x^2})^{10} \) is: \[ \boxed{13440 x^{-2}} \]
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