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If X + 1 by x is equal to 3 then x cube + 1 by x cube is equal to what

Answer»

Hello !!

X + 1/X = 3

Cubing on both sides,

( X + 1/X )³ = (3)³

Using identity ,

( A + B)³ = (A)³ + (B)³ + 3AB ( A + B ).

( X )³ + 1/X³ + 3X × 1/X ( X + 1/X ) = 27

X³ + 1/X³ + 3 × 3 = 27



X³ + 1/X³ = 27 - 9


X³ + 1/X³ = 18.



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