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Mathematics

x2+1x23x^2 + \dfrac{1}{x^2} - 3 in the form of factors is :

  1. (x1x)(x+1x)\Big(x - \dfrac{1}{x}\Big)\Big(x + \dfrac{1}{x}\Big) - 1

  2. (x+1x+1)(x1x1)\Big(x + \dfrac{1}{x} + 1\Big)\Big(x - \dfrac{1}{x} - 1\Big)

  3. (x1x)(x1x1)\Big(x - \dfrac{1}{x}\Big)\Big(x - \dfrac{1}{x} - 1\Big)

  4. (x1x+1)(x1x1)\Big(x - \dfrac{1}{x} + 1\Big)\Big(x - \dfrac{1}{x} - 1\Big)

Factorisation

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Answer

Given,

=x2+1x23=x2+1x221=x2+1x2(2×x×1x)1=[x2+1x2(2×x×1x)]1=(x1x)21=(x1x)212=(x1x+1)(x1x1).\phantom{=}x^2 + \dfrac{1}{x^2} - 3 \\[1em] = x^2 + \dfrac{1}{x^2} - 2 - 1 \\[1em] = x^2 + \dfrac{1}{x^2} - \Big(2 \times x \times \dfrac{1}{x}\Big) - 1 \\[1em] = \Big[x^2 + \dfrac{1}{x^2} - \Big(2 \times x \times \dfrac{1}{x}\Big)\Big] - 1 \\[1em] = \Big(x - \dfrac{1}{x}\Big)^2 - 1 \\[1em] = \Big(x - \dfrac{1}{x}\Big)^2 - 1^2 \\[1em] = \Big(x - \dfrac{1}{x} + 1\Big)\Big(x - \dfrac{1}{x} - 1\Big).

Hence, Option 4 is the correct option.

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