Question : If $\left(x^2+\frac{1}{x^2}\right)=7$, and $0<x<1$, find the value of $x^2-\frac{1}{x^2}$.
Option 1: $3 \sqrt{5}$
Option 2: $4 \sqrt{5}$
Option 3: $-4\sqrt{3}$
Option 4: $-3\sqrt{5}$
Latest: SSC CGL Tier 1 Result 2024 Out | SSC CGL preparation tips to crack the exam
Don't Miss: SSC CGL Tier 1 Scorecard 2024 Released | SSC CGL complete guide
Suggested: Month-wise Current Affairs | Upcoming Government Exams
Correct Answer: $-3\sqrt{5}$
Solution : $(x-\frac{1}{x})^{2}=(x^2+\frac{1}{x^2}-2)$ ⇒ $(x-\frac{1}{x})^{2}=7-2$ ⇒ $(x-\frac{1}{x})^{2}=5$ ⇒ $(x-\frac{1}{x})=-\sqrt{5}$ since $0<x<1$ Again, $(x+\frac{1}{x})^{2}=(x^2+\frac{1}{x^2}+2)$ ⇒ $(x+\frac{1}{x})^{2}=(7+2)$ ⇒ $(x+\frac{1}{x})^{2}=9$ ⇒ $(x+\frac{1}{x})=3$ since $0<x<1$ Now we know $(x-\frac{1}{x})(x+\frac{1}{x})= x^2-\frac{1}{x^2}$ ⇒ $x^2-\frac{1}{x^2}=-\sqrt{5}\times 3$ ⇒ $x^2-\frac{1}{x^2}=-3\sqrt{5}$. Hence the correct answer is $-3\sqrt{5}$.
Candidates can download this ebook to know all about SSC CGL.
Result | Eligibility | Application | Selection Process | Preparation Tips | Admit Card | Answer Key
Question : If $x+\left [\frac{1}{(x+7)}\right]=0$, what is the value of $x-\left [\frac{1}{(x+7)}\right]$?
Question : If $x^2-7 x+1=0$ and $0<x<1$, what is the value of $x^2-\frac{1}{x^2}?$
Question : If $\left(x^2+\frac{1}{x^2}\right)=6$ and $0<x<1$, what is the value of $x^4-\frac{1}{x^4}$?
Question : If $x+\frac{1}{x}=\sqrt{3}$, the value of $\left (x^{3}+\frac{1}{x^{3}} \right )$ is:
Question : If $x^2-\sqrt{7} x+1=0$, then what is the value of $x^5+\frac{1}{x^5} ?$
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile