Question

a=9-2*radical 14* *totul sub radical*

Answer 1

$9-2 \sqrt{14} =7-2 \sqrt{7}\cdot \sqrt{2} +2= ( \sqrt{7}) ^{2} -2 \sqrt{7}\cdot \sqrt{2}+ ( \sqrt{2}) ^{2} = \\ =( \sqrt{7}- \sqrt{2} ) ^{2} \\ \sqrt{9-2 \sqrt{14} }= \sqrt{7} - \sqrt{2}$