[pont494]

$xy=1----->29xy=29$
$x=(\sqrt{2} +1)^2=3+2\sqrt{2} ,y=(\sqrt{2} -1)^2=3-2\sqrt{2} $
$x+y=6$
$\sqrt{(x^2+2xy+y^2)+29xy+16} $
$=\sqrt{(x+y)^2+29xy+16} $
$=\sqrt{6^2+29+16} $
$=\sqrt{81} = 9$