SSC CGL 7 Sep 2016 Paper

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Question : 61 of 100

Marks: +1, -0

If

a/b+b/a

= 1, then the value of

a^3 + b^3

will be

1
0
–1
2

Solution:

a/b+b/a

= 1
⇒

{a^2+b^2}/{ab}

= 1
⇒

a^2+b^2

= ab
⇒

a^2

- ab +

b^2

= 0
∴

a^3 + b^3

= (a + b)

(a^2-ab+b^2)

= 0

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