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Question Number 139113 by mathdanisur last updated on 22/Apr/21

$$if,x=3+\sqrt{7}$$$$find,\frac{1}{\sqrt{8x^2-1}}$$

Answered by MJS_new last updated on 22/Apr/21

$$\frac{1}{\sqrt{8x^2-1}}=\frac{1}{\sqrt{127+48\sqrt{7}}}=\sqrt{127-48\sqrt{7}}$$$${(a+b\sqrt{7})}^2=127-48\sqrt{7}\Rightarrow a=8\wedge b=-3$$$$\Rightarrow \mathrm{answer}\mathrm{is}8-3\sqrt{7}$$

Commented by mathdanisur last updated on 22/Apr/21

$$thankssir$$

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