\( * \) Term involuing \( x^{2} \) in the expanson of \[ \left(2 x-\frac{1}{2 x}\right)^{12} \]
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Bonus Knowledge
To find the term involving \( x^2 \) in the expansion of \( \left(2x - \frac{1}{2x}\right)^{12} \), we use the binomial theorem. The general term in the expansion can be given by: \[ T_k = \binom{12}{k} (2x)^{12-k} \left(-\frac{1}{2x}\right)^k \] This simplifies to: \[ T_k = \binom{12}{k} (2^{12-k})(-1)^k \left(\frac{1}{2^k}\right) x^{12-k-k} = \binom{12}{k} (-1)^k 2^{12-2k} x^{12-2k} \] To find the term that contains \( x^2 \), we set the exponent of \( x \) equal to 2: \[ 12 - 2k = 2 \implies 10 = 2k \implies k = 5 \] Substituting \( k = 5 \) into \( T_k \): \[ T_5 = \binom{12}{5} (-1)^5 2^{12-2 \cdot 5} x^2 = -\binom{12}{5} 2^2 x^2 = -\binom{12}{5} \cdot 4 x^2 \] Calculating \( \binom{12}{5} = 792 \): \[ T_5 = -792 \cdot 4 x^2 = -3168 x^2 \] Thus, the term involving \( x^2 \) is \( -3168 x^2 \).