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The term independent of x in the expansi...

The term independent of `x` in the expansion of `((1)/(60)-(x^(8))/(81)).(2x^(2)-(3)/(x^(2)))^(6)` is equal to:

A

36

B

-72

C

-36

D

-108

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The correct Answer is:
To find the term independent of \( x \) in the expansion of \[ \left(\frac{1}{60} - \frac{x^8}{81}\right) \left(2x^2 - \frac{3}{x^2}\right)^6, \] we will follow these steps: ### Step 1: Expand the expression We can rewrite the expression as: \[ \frac{1}{60} \left(2x^2 - \frac{3}{x^2}\right)^6 - \frac{x^8}{81} \left(2x^2 - \frac{3}{x^2}\right)^6. \] ### Step 2: Use the Binomial Theorem Using the Binomial Theorem, we can expand \( \left(2x^2 - \frac{3}{x^2}\right)^6 \): \[ \left(2x^2 - \frac{3}{x^2}\right)^6 = \sum_{r=0}^{6} \binom{6}{r} (2x^2)^r \left(-\frac{3}{x^2}\right)^{6-r}. \] This simplifies to: \[ = \sum_{r=0}^{6} \binom{6}{r} 2^r (-3)^{6-r} x^{2r} x^{-2(6-r)} = \sum_{r=0}^{6} \binom{6}{r} 2^r (-3)^{6-r} x^{2(2r - 6)}. \] ### Step 3: Identify the term independent of \( x \) We need to find the term where the exponent of \( x \) is zero: \[ 2(2r - 6) = 0 \implies 2r - 6 = 0 \implies r = 3. \] ### Step 4: Calculate the coefficient for \( r = 3 \) Substituting \( r = 3 \) into the binomial expansion gives: \[ \binom{6}{3} 2^3 (-3)^{3} = 20 \cdot 8 \cdot (-27) = -4320. \] ### Step 5: Calculate the contribution from both parts Now, we substitute \( r = 3 \) into both parts of the original expression: 1. From the first part: \[ \frac{1}{60} \cdot (-4320) = -72. \] 2. From the second part, we need to find the term independent of \( x \) when \( r = 3 \) as well: The term for \( r = 3 \) in the second part is: \[ -\frac{x^8}{81} \cdot \binom{6}{3} 2^3 (-3)^{3} = -\frac{x^8}{81} \cdot (-4320). \] This term will not contribute to the independent term since it involves \( x^8 \). ### Step 6: Combine the contributions Thus, the only contribution to the independent term comes from the first part: \[ -72. \] ### Final Answer The term independent of \( x \) in the expansion is \[ \boxed{-72}. \]

To find the term independent of \( x \) in the expansion of \[ \left(\frac{1}{60} - \frac{x^8}{81}\right) \left(2x^2 - \frac{3}{x^2}\right)^6, \] we will follow these steps: ...
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