6.
√(xy)=2
√(7-3√5)y=2 l²
(7-3√5)y=4 =>y=4/(7-3√5)
Rationalizam numitorul
y=4(7+3√5)/(49-45)
y=4(7+3√5)/4 =>y=7+3√5
M.a.=(7-3√5+7+3√5)/2=14/2=7
10.
[(2-2√2+1)/(2-1) + (2+2√2+1)/(2-1)]⁻² + [(3-√6+2)/(3-2) + (3+√6+2)/(3-2)]⁻²=
(3-2√2+3+2√2)⁻² +(5-√6+5+√6)⁻² =
6⁻² +10⁻² =
1/6² + 1/10²=
1/36 + 1/100=
36=2²·3²
100=2²·5²
________
c.m.m.m.c.=2²·3²·5²=900
5²/900 + 3²/900=
(25+9)/900=
34/900=17/450
