Răspuns:
[tex]ma = \frac{x + y}{2} [/tex]
[tex]= \frac{2 \sqrt{8} - \sqrt{7} + 7 \sqrt{7} - 2 \sqrt{2} }{2} [/tex]
[tex]= \frac{2 \times 2 \sqrt{2} - 2 \sqrt{2} + 7 \sqrt{7} - \sqrt{7} }{2} [/tex]
[tex] = \frac{(4 - 2) \sqrt{2} + (7 - 1) \sqrt{7} }{2} [/tex]
[tex]= \frac{2 \sqrt{2} + 6 \sqrt{7} }{2} = \sqrt{2} + 3 \sqrt{7} [/tex]
