If a^2+\frac{1}{a^2}=27, then the value of a-\frac{1}{a} is

Sainik School Entrance Exam 2019 Solved Paper

Question : 21 of 150

Marks: +1, -0

a^2+{1}/{a^2}=27

, then the value of

a-{1}/{a}

Solution:

(d)

a^2+1/a^2=27

On subtracting 2 from both sides,

a^2+1/a^2-2=27-2

a^2+1/a^2-2.a.1/a=25

(a-1/1)^2=25

a-1/a=√25

a-1/a=±5.

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