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Mathematics

If a21a2=5, evaluate a4+1a4a^2 - \dfrac{1}{a^2} = 5, \text{ evaluate } a^4 + \dfrac{1}{a^4}.

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Answer

We know that,

a4+1a4=(a21a2)2+2a^4 + \dfrac{1}{a^4} = \Big(a^2 - \dfrac{1}{a^2}\Big)^2 + 2

Substituting values we get,

a4+1a4=(5)2+2=25+2=27.a^4 + \dfrac{1}{a^4} = (5)^2 + 2 = 25 + 2 = 27.

Hence, a4+1a4=27.a^4 + \dfrac{1}{a^4} = 27.

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