Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If x4 + x-4 = 194, x > 0

Find (x - 2)2.

Options:

1

2

-3

3

Correct Answer:

3

Explanation:

Formula → x4 + \(\frac{1}{x^4}\) = a

            →  x2 + \(\frac{1}{x^2}\) = \(\sqrt {a + 2}\)

 

x4 + \(\frac{1}{x^4}\) = 194

x2 + \(\frac{1}{x^2}\) = \(\sqrt {194 + 2}\) = 14

x + \(\frac{1}{x}\) = \(\sqrt {14 + 2}\) = 4

x2 + 1 = 4x

x2 - 4x = -1

Now, we have to find (x - 2)2 

 x2 - 4x + 4 = -1 + 4 = 3