Question

If x-1/x=⅓, evaluate x³-1/x³
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Answer 1

Answer:

28/27

Step-by-step explanation:

Using:

( a - b )³ = a³ - b³ - 3ab( a - b )

= > ( x - 1/x )³ = (1/3)³

= > x³ - 1/x³ - 3(x*1/x)( x - 1/x ) = 1/27

= > x³ - 1/x³ - 3(1)(1/3) = 1/27

= > x³ - 1/x³ - 1 = 1/27

= > x³ - 1/x³ = 1/27 + 1

= > x³ - 1/x³ = (1+27)/27 = 28/27