X+1/X=√5, then the value of X³+1/ X³ is:

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X+1/X=√5,ആയാൽ X³+1/ X³=?

A10√5

B2√5

C5√5

DNone of these

Answer:

X+1/X=√5 a³ + b³ = (a + b)³ - 3ab(a + b) X³ + 1/ X³ = (X+1/X)³ - 3X × 1/X × (X+1/X) = (X+1/X)³ - 3(X+1/X) = (√5)³ - 3(√5) = 5√5 - 3√5 = 2√5

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