Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If x2 - 10x - 1= 0

 and x > 1, then the value of

x3 - \(\frac{1}{x^3}\) will be:

Options:

1030

1234

1095

970

Correct Answer:

1030

Explanation:

If x2 - 10x - 1= 0

Divide by x on both sides,

x -  \(\frac{1}{x}\) = 10

x3 - \(\frac{1}{x^3}\)  = 103 + 3 × 10 = 1030

 

Note - if x -  \(\frac{1}{x}\) = a

then x3 - \(\frac{1}{x^3}\) =  a3 + 3a