If x4 + \(\frac{1}{x^4}\) = 27887, the positive value of ( x + \(\frac{1}{x}\) -3 ) is?
Answer & explanation
Correct answer: option 4
If x4 + \(\frac{1}{x^4}\) = a
then x2 + \(\frac{1}{x^2}\) = \(\sqrt {a + 2}\) = b
and x + \(\frac{1}{x}\) = \(\sqrt {b + 2}\)
ATQ,
x4 + \(\frac{1}{x^4}\) = 27887
x2 + \(\frac{1}{x^2}\) = \(\sqrt {27887 + 2}\) = 167
So, ( x + \(\frac{1}{x}\) - 3 ) = ( \(\sqrt {167 + 2}\) - 3 ) = 10