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Question : If $a+\frac{1}{a}=5$, then what is the value of $a^3+\frac{1}{a^3} ?$

Option 1: 110

Option 2: 15

Option 3: 105

Option 4: –10


Team Careers360 22nd Jan, 2024
Answer (1)
Team Careers360 24th Jan, 2024

Correct Answer: 110


Solution : Given, $a+\frac{1}{a}=5$
Cubing both sides,
$(a+\frac{1}{a})^3=125$
⇒ $a^3+\frac{1}{a^3}+3(a)(\frac{1}{a})(a+\frac{1}{a})=125$
⇒ $a^3+\frac{1}{a^3}+3(1)(5)=125$
⇒ $a^3+\frac{1}{a^3}=110$
Hence, the correct answer is 110.

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