ข้อ4
$1-\sqrt{6} +\frac{1+3\sqrt{2}+\sqrt{3}+\sqrt{6} }{1+\sqrt{2} +2\sqrt{3} +\sqrt{6} }$
= $1-\sqrt{6} +\frac{(1+\sqrt{3})+(\sqrt{6} +3\sqrt{2} ) }{(1+\sqrt{2})+(6+2\sqrt{3} ) }$=$1-\sqrt{6} +\frac{1+\sqrt{3}+\sqrt{6}(1+\sqrt{3} ) }{1+\sqrt{2}+\sqrt{6}(1+\sqrt{2} ) } $
=$1-\sqrt{6}+\frac{(1+\sqrt{3})(1+\sqrt{6} ) }{(1+\sqrt{2})(1+\sqrt{6} ) } $
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