if-x-3-7-find-1-8x-2-1-

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

i f, x = 3 + \sqrt{7}

f i n d, \frac{1}{\sqrt{8 x^{2} - 1}}

Answered by MJS_new last updated on 22/Apr/21

\frac{1}{\sqrt{8 x^{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 \land b = - 3

\Rightarrow answer is 8 - 3 \sqrt{7}

Commented by mathdanisur last updated on 22/Apr/21

t h a n k s s i r