Răspuns :
[tex]\it 8\sqrt7-\Big(\dfrac{1}{2}\sqrt7+8\sqrt7-\dfrac{5}{6}\sqrt7\Big)=\sqrt7(8-\dfrac{^3)1}{\ 2}-8+\dfrac{5}{6})=\sqrt7\cdot\dfrac{-3+5}{6}=\\ \\ \\ =\sqrt7\cdot\dfrac{\ 2^{(2}}{6}=\sqrt7\cdot\dfrac{1}{3}=\dfrac{\sqrt7}{3}[/tex]
[tex]\it 8\sqrt7-\Big(\dfrac{1}{2}\sqrt7+8\sqrt7-\dfrac{5}{6}\sqrt7\Big)=\sqrt7(8-\dfrac{^3)1}{\ 2}-8+\dfrac{5}{6})=\sqrt7\cdot\dfrac{-3+5}{6}=\\ \\ \\ =\sqrt7\cdot\dfrac{\ 2^{(2}}{6}=\sqrt7\cdot\dfrac{1}{3}=\dfrac{\sqrt7}{3}[/tex]