Răspuns :
[tex]( \frac{7}{2 \sqrt{2} } - \frac{5 \sqrt{2} }{8} )*4 \\ \\ ( \frac{7 \sqrt{2} }{4}- \frac{5 \sqrt{2} }{8})*4 \\ \\ \frac{9 \sqrt{2} }{8} *4 \\ \\ \frac{9 \sqrt{2} }{2} [/tex]
[tex]\Big(^{\big{\sqrt2)}}\dfrac{7}{2\sqrt2}-\dfrac{5\sqrt2}{8}\Big)\cdot 4 = \\ \\ = \Big(\dfrac{7\sqrt2}{2\cdot 2}-\dfrac{5\sqrt2}{8}\Big)\cdot 4 = \\ \\ = \Big(^{\big{2)}}\dfrac{7\sqrt2}{4}-\dfrac{5\sqrt2}8}\Big)\cdot 4 = \\ \\ =\Big(\dfrac{14\sqrt2}{8}-\dfrac{5\sqrt2}{8}\Big)\cdot 4 \\ \\ = \Big(\dfrac{14\sqrt2-5\sqrt2}{8}\Big)\cdot 4 = \\ \\ = \dfrac{9\sqrt2}{2}[/tex]