Question : If $x^2-4 x-1=0$, then find the value of $x^2+\frac{1}{x^2}-5$.
Option 1: 17
Option 2: 12
Option 3: 15
Option 4: 13
New: SSC CHSL Tier 2 answer key released | SSC CHSL 2024 Notification PDF
Recommended: How to crack SSC CHSL | SSC CHSL exam guide
Don't Miss: Month-wise Current Affairs | Upcoming government exams
Correct Answer: 13
Solution :
$x^2-4 x-1=0$
$x-\frac{1}{x} = 4$
Squaring on both sides,
$ x^{2} + \frac{1}{x^{2}} - 2×x×\frac{1}{x} = 16$
$ x^{2} + \frac{1}{x^{2}} = 16+2 = 18$ -----------(i)
Now, $x^2+\frac{1}{x^2}-5$
= 18 – 5
= 13
Hence, the correct answer is 13.
Related Questions
Know More about
Staff Selection Commission Combined High ...
Result | Eligibility | Application | Admit Card | Answer Key | Preparation Tips | Cutoff
Get Updates Brochure
Your Staff Selection Commission Combined Higher Secondary Level Exam brochure has been successfully mailed to your registered email id “”.
