4.阅读下列解题过程:
$\frac{1}{\sqrt{2}+1}$=$\frac{1×(\sqrt{2}-1)}{(\sqrt{2}+1)×(\sqrt{2}-1)}$=$\frac{\sqrt{2}-1}{(\sqrt{2})^{2}-{1}^{2}}$=$\sqrt{2}$-1;
$\frac{1}{\sqrt{3}+\sqrt{2}}$=$\frac{1×(\sqrt{3}-\sqrt{2})}{(\sqrt{3}+\sqrt{2})(\sqrt{3}-\sqrt{2})}$=$\frac{\sqrt{3}-\sqrt{2}}{(\sqrt{3})^{2}-(\sqrt{2})^{2}}$=$\sqrt{3}$-$\sqrt{2}$
请回答下列问题:
(1)归纳:观察上面的解题过程,请直接写出下列各式的结果.
①$\frac{1}{\sqrt{7}+\sqrt{6}}$=$\sqrt{7}$-$\sqrt{6}$;②$\frac{1}{\sqrt{n}+\sqrt{n-1}}$=$\sqrt{n}$-$\sqrt{n-1}$;
(2)应用:求$\frac{1}{\sqrt{2}+1}$+$\frac{1}{\sqrt{3}+\sqrt{2}}$+$\frac{1}{\sqrt{4}+\sqrt{3}}$+$\frac{1}{\sqrt{5}+\sqrt{4}}$+…+$\frac{1}{\sqrt{10}+\sqrt{9}}$的值;
(3)拓广:$\frac{1}{\sqrt{3}-1}$-$\frac{1}{\sqrt{5}-\sqrt{3}}$+$\frac{1}{\sqrt{7}-\sqrt{5}}$-$\frac{1}{\sqrt{9}-\sqrt{7}}$=-1.