Question

If X + 1/x = 5/2, Then x^3 - 1/x^3 = ?

Answer 1

Answer:

63/8

Step-by-step explanation:

Square on both sides,

=> (x + 1/x)² = (2.5)²

=> x² + 1/x² + 2 = 6.25

=> x² + 1/x² = 4.25

Therefore,

(x - 1/x)² = x² + 1/x² - 2 = 4.25 - 2

(x - 1/x)² = 2.25

x - 1/x = 1.5

Hence, x³ - 1/x³ :

=> (x - 1/x)(x² + 1/x² + 1)

=> (1.5)(4.25 + 1)

=> (1.5)(5.25)

=> 7.875 or 63/8

Answer 2

Answer:

7.875 or 63/8

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