SSC CHSL 6 Mar 2018 Shift 3 Paper

Section: English Language

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Question : 4 of 100

Marks: +1, -0

What is the value of

x^3-1/x^3+8

when

8x −8 / x − 16 = 0

?

14
8
16
22

Solution:

Given :

8x −8 / x − 16 = 0

⇒

x-1/x=2

--------------(i)
Cubing both sides, we get :
⇒

(x − 1/x)^3 = (2)^ 3

⇒

(x^ 3 − 1/x^ 3 ) − 3(x)( 1/x)(x − 1/x) = 8

Substituting value from equation (i),
⇒

(x ^3 − 1/x ^3 ) − 3(1)(2)=8

⇒

x^ 3 − 1/x ^3 = 8 + 6 = 14

∴

x^3 − 1/x ^3 + 8 = 22

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