Question 75

If $$x^4 + x^{-4} = 2207, (x > 0)$$ then the value of $$x + x^{-1}$$ is:

Solution

$$x^4 + x^{-4} = 2207$$

$$(x^2 + x^{-2})^2$$ - 2$$(x^2)(x^{-2})$$ = 2207

$$(x^2 + x^{-2})^2$$ - 2 = 2207

$$(x^2 + x^{-2})^2$$ = 2209

Square root of both sides,

$$(x^2 + x^{-2})$$ = 47

Again,

$$(x + x^{-1})^2$$ - 2$$(x^1)(x^{-1})$$ = 47

$$(x + x^{-1})^2$$ - 2 =47

$$(x + x^{-1})^2$$ = 49

Square root of both sides,

$$(x + x^{-1})$$ = 7


Create a FREE account and get:

  • Free SSC Study Material - 18000 Questions
  • 230+ SSC previous papers with solutions PDF
  • 100+ SSC Online Tests for Free

cracku

Boost your Prep!

Download App