a. Quantitative Ability

Find the value

Tagged: algebra, positive

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November 1, 2011 at 9:02 pm #2907
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Q. if a is positive and a^4 – 62a^2 +1 = 0 ; find a^3 +1/a^3
424
648
392
488
November 1, 2011 at 9:04 pm #3022
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Keymaster
a⁴– 62a² + 1 = 0

Dividing by a² we get
=> a² + 1/a² = 62
=> (a + 1/a) = 8

a³ + 1/a³ = (a + 1/a)(a² – 1 + 1/a²) = 8x(62-1) = 488 Answer
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