Keerthana
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If x=5+26x=5+2 \sqrt{6}, then x1x\frac{x-1}{\sqrt{x}} is equal to :

a

232 \sqrt{3}

b

2\sqrt{2}

c

222 \sqrt{2}

d

3\sqrt{3}

Answer : Option C
Explanation :

x=5+26x=5+2 \sqrt{6}

=5+2×3×2=5+2 \times \sqrt{3} \times \sqrt{2}

=3+2+2×3×2=3+2+2 \times \sqrt{3} \times \sqrt{2}

=(3+2)2=(\sqrt{3}+\sqrt{2})^{2}

x=3+2\therefore \quad \sqrt{x}=\sqrt{3}+\sqrt{2}

1x=13+2\therefore \quad \frac{1}{\sqrt{x}}=\frac{1}{\sqrt{3}+\sqrt{2}}

=32(3+2)(32)=32=\frac{\sqrt{3}-\sqrt{2}}{(\sqrt{3}+\sqrt{2})(\sqrt{3}-\sqrt{2})}=\sqrt{3}-\sqrt{2}

x1x\therefore \frac{x-1}{\sqrt{x}}

=(5+261)(32)=(5+2 \sqrt{6}-1)(\sqrt{3}-\sqrt{2})

=(4+26)(32)=(4+2 \sqrt{6})(\sqrt{3}-\sqrt{2})

=43+21842212=4 \sqrt{3}+2 \sqrt{18}-4 \sqrt{2}-2 \sqrt{12}

=43+624243=4 \sqrt{3}+6 \sqrt{2}-4 \sqrt{2}-4 \sqrt{3}

=22=2 \sqrt{2}

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