Question : If $(y-\frac{1}{y})=-9$, what will be the value of $(y^5-\frac{1}{y^5})?$
Option 1: – 62757
Option 2: – 62748
Option 3: – 62739
Option 4: – 59049
Recommended: How to crack SSC CHSL | SSC CHSL exam guide
Don't Miss: Month-wise Current Affairs | Upcoming government exams
Correct Answer: – 62739
Solution :
$(y-\frac{1}{y})=-9$
Squaring on both sides,
⇒ $(y-\frac{1}{y})^2=(-9)^2$
⇒ $y^2+\frac{1}{y^2}-2×y×\frac{1}{y}=(-9)^2$
⇒ $y^2+\frac{1}{y^2}= 81+2= 83$
Squaring on both sides,
$(y^2+\frac{1}{y^2})^2$ = $83^2$
⇒ $y^4+\frac{1}{y^4}+2 = 6889$
⇒ $y^4+\frac{1}{y^4} = 6887$
⇒ $(y-\frac{1}{y})(y^4+\frac{1}{y^4})$ = $(y^5-\frac{1}{y^5}-y^3+\frac{1}{y^3})$
⇒ $-9×6887 = (y^5-\frac{1}{y^5}-(y^3-\frac{1}{y^3}))$
⇒ $-9×6887 = [y^5-\frac{1}{y^5}-(y-\frac{1}{y})(y^2+\frac{1}{y^2}+y×\frac{1}{y})]$
⇒ $-61983 = [y^5-\frac{1}{y^5}-(-9)(83+1)]$
⇒ $y^5-\frac{1}{y^5} = -61983-756 = - 62739$
Hence, the correct answer is – 62739.
Related Questions
Know More about
Staff Selection Commission Combined High ...
Answer Key | Eligibility | Application | Admit Card | Preparation Tips | Result | Cutoff
Get Updates BrochureYour Staff Selection Commission Combined Higher Secondary Level Exam brochure has been successfully mailed to your registered email id “”.




