Sainik School Entrance Exam 2021 Solved Paper

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Question : 40 of 150

Marks: +1, -0

If

\frac{a}{b}-{b}/{a}=2

, then

a^3-b^3=

1
$-1$
0
2

Solution:

(c)

{a}/{b}-{b}/{a}=-2

⇒ {a^2-b^2}/{a b}=-2

⇒ a^2-b^2=-2 a b ⇒a^2-b^2+2 a b=0

⇒ (a-b)^2=0

Taking square root on both sides,

(a-b)=0

Now,

a^3-b^3=(a-b)(a^2+b^2+a b)

Putting the value of

(a-b)

from Eqn. (1)

a^3-b^3=0

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