If a^2 + 1 = 9a, (a ≠ 0) then the value of (a)2 + 1/(a)^2 is

SSC CGL 2 Sep 2016 Shif 2 Paper

Question : 59 of 100

Marks: +1, -0

a^2

+ 1 = 9a, (a ≠ 0) then the value of (a)2 +

1/(a)^2

Solution:

a^2

+ 1 = 9a
⇒

{a^2+1}/a

= 9
⇒ a +

1/a

= 9
On squaring both sides,

a^2+1/a^2

+ 2 = 81
⇒

a^2+1/a^2

= 81 - 2 = 79

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