a=3✓5+1
b=3✓5-1
media aritmetică
ma= (a+b)/2
[tex]ma = \frac{3 \sqrt{5} + 1 + 3 \sqrt{5} - 1}{2} = \frac{6 \sqrt{5} }{2} = 3 \sqrt{5} [/tex]
media geometrică
mg=✓a•b
[tex]mg = \sqrt{(3 \sqrt{5} + 1) \times (3 \sqrt{5} -1 ) } \\ (a + b)(a - b) = {a}^{2} - {b}^{2} \\ mg = \sqrt{(3 \sqrt{5) } {}^{2} - {1}^{2} } = \sqrt{9 \times 5 - 1} \\ mg = \sqrt{45 - 1} = \sqrt{44} = 2 \sqrt{11} [/tex]
