সাধারণ পদ , মধ্যপদ ও সমদূরবর্তী পদ নির্ণয়
The term independent of x in the expansion of (x−14)4(x+1x)3\displaystyle \left ( x -\dfrac{1}{4} \right )^4\left ( x + \dfrac{1}{x} \right )^3(x−41)4(x+x1)3
19/16
0
14
none of these
(x−1x)4(x+1x)3=(x−1x)(x−1x)3(x+1x)3=(x−1x){(x−1x)(x+1x)}3=(x−1x)(x2−1x2)3=(x−1x)(x6−1x6−3x4×1x2+3x2×1x4)=(x−1x)(x6−1x6−3x2+3x2)=x7−1x5−3x3+3x−x5+1x7+3x−3x3+0 \begin{aligned} & \left(x-\frac{1}{x}\right)^{4}\left(x+\frac{1}{x}\right)^{3} \\ = & \left(x-\frac{1}{x}\right)\left(x-\frac{1}{x}\right)^{3}\left(x+\frac{1}{x}\right)^{3} \\ = & \left(x-\frac{1}{x}\right)\left\{\left(x-\frac{1}{x}\right)\left(x+\frac{1}{x}\right)\right\}^{3} \\ = & \left(x-\frac{1}{x}\right)\left(x^{2}-\frac{1}{x^{2}}\right)^{3} \\ = & \left(x-\frac{1}{x}\right)\left(x^{6}-\frac{1}{x^{6}}-3 x^{4} \times \frac{1}{x^{2}}+3 x^{2} \times \frac{1}{x^{4}}\right) \\ = & \left(x-\frac{1}{x}\right)\left(x^{6}-\frac{1}{x^{6}}-3 x^{2}+\frac{3}{x^{2}}\right) \\ = & x^{7}-\frac{1}{x^{5}}-3 x^{3}+\frac{3}{x}-x^{5}+\frac{1}{x^{7}}+3 x-\frac{3}{x^{3}}+0 \end{aligned} ======(x−x1)4(x+x1)3(x−x1)(x−x1)3(x+x1)3(x−x1){(x−x1)(x+x1)}3(x−x1)(x2−x21)3(x−x1)(x6−x61−3x4×x21+3x2×x41)(x−x1)(x6−x61−3x2+x23)x7−x51−3x3+x3−x5+x71+3x−x33+0
⇒ \Rightarrow ⇒ Term independent of x=0 x=0 x=0
Hence the correct option is B.
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