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If \( \Large a+\frac{1}{a}=\sqrt{3} \), then the value of \( \Large a^{6}-\frac{1}{a^{6}}+2 \) will be
A) \( \Large 3\sqrt{3} \)
B) 5
C) 1
D) 2
Correct answer:
D) 2
Description for Correct answer:
\( \Large a+\frac{1}{a}=\sqrt{3} \)
On squaring both sides
=>\( \Large a^{2}+\frac{1}{a^{2}}+2=\sqrt{3} \)
=>\( \Large a^{2}+\frac{1}{a^{2}}=1 \)
Now, multiplying Eqs. (i) and (ii),
\( \Large \left(a+\frac{1}{a}\right) \left(a^{2}+\frac{1}{a^{2}}\right)=\sqrt{3} \)
=>\( \Large a^{3}+\frac{a}{a^{2}}+\frac{a^{2}}{a}+\frac{1}{a^{3}}=\sqrt{3} \)
=>\( \Large a^{3}+\frac{1}{a^{3}}+ \left(\frac{1}{a}+a\right)=\sqrt{3} \)
=>\( \Large a^{3}+\frac{1}{a^{3}}+\sqrt{3}=\sqrt{3} \) [from Eq. (i)]
=>\( \Large a^{3}+\frac{1}{^{3}}=0 \)
=>\( \Large a^{6}= -1 \)
Therefore, \( \Large a^{6}-\frac{1}{a^{6}}+2 = \left(-1\right)^{6}-\frac{1}{ \left(-1\right)^{6}}+2 \)
= 1-1+2=2
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