解：?$(1)\frac {1}{1+\sqrt{2}}=\frac {1-\sqrt{2}}{(1+\sqrt{2})(1-\sqrt{2})}=-(1-\sqrt{2})=-1+\sqrt{2}$?
?$(2)\frac 1{\sqrt{n}+\sqrt{n+1}}=-\sqrt{n}+\sqrt{n+1}$?
?$(3)$?原式?$=(-1+\sqrt{2}-\sqrt{2}+\sqrt{3}-\sqrt{3}+\sqrt{4}+...-\sqrt{2014}+\sqrt{2015})×(1+\sqrt{2015})$?
?$ =(-1+\sqrt{2015})(1+\sqrt{2015})$?
?$ =2015-1$?
?$ =2014$?
