If x-1/x=2, then the value of following is: x^3 − 1/x ^3 =?

SSC CHSL 15 Nov 2015 Shift 1 Paper

Question : 107 of 199

Marks: +1, -0

x-1/x=2,

then the value of following is:

x^3 − 1/x ^3 =?

Solution:

Given :

x-1/x=2

Cubing both sides, we get :
⇒

(x-1/x)^3=(2)^3

⇒

x ^3 − 1/x ^3 − 3(x)( 1/x) = 8

⇒

x ^3 − 1/x ^3 − 3 = 8

x ^3 − 1/x ^3 = 8+ 3 =11

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