SSC CGL 10 Aug 2017 Shift 1 Paper

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Question : 63 of 100

Marks: +1, -0

If

3a - (3 / a) - 3 = 0

, then what is the value of

a^3 - (1 / a^3) + 2

?

0
2
4
6

Solution:

3a - (3 / a) - 3 = 0

⇒

3(a -1 / a -1) = 0

⇒

a -1 / a -1=0

⇒

a -1 / a =1

On cubing both sides.

a ^3-1 / a^3 -3(a-1/a)=1

⇒

a ^3-1 / a^3-3=1

⇒

a ^3-1 / a^3=4

⇒

a ^3-1 / a^3+2=4+2

∴

a ^3-1 / a^3+2=6

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