3.
\(21.\)阅读下列材料,然后解答下列问题:
在进行代数式化简时,我们有时会碰上如\( \dfrac{5}{ \sqrt{3}}\),\( \dfrac{2}{ \sqrt{3}+1}\)这样的式子,其实我们还可以将其进一步化简:
\((\)一\() \dfrac{5}{ \sqrt{3}}= \dfrac{5× \sqrt{3}}{ \sqrt{3}× \sqrt{3}}= \dfrac{5}{3} \sqrt{3}\);
\((\)二\() \dfrac{2}{ \sqrt{3}+1}= \dfrac{2×( \sqrt{3}-1)}{( \sqrt{3}+1)( \sqrt{3}-1)}= \dfrac{2( \sqrt{3}-1)}{( \sqrt{3})^{2}-1}= \sqrt{3}-1\);
\((\)三\() \dfrac{2}{ \sqrt{3}+1}= \dfrac{3-1}{ \sqrt{3}+1}= \dfrac{( \sqrt{3})^{2}-1^{2}}{ \sqrt{3}+1}= \dfrac{( \sqrt{3}+1)( \sqrt{3}-1)}{ \sqrt{3}+1}= \sqrt{3}-1\)
以上这种化简的方法叫分母有理化.
\((1)\)请用不同的方法化简\( \dfrac{2}{ \sqrt{5}+ \sqrt{3}}\):
\(①\)参照\((\)二\()\)式化简\( \dfrac{2}{ \sqrt{5}+ \sqrt{3}}=\)_____________________________________________
\(②\)参照\((\)三\()\)式化简\( \dfrac{2}{ \sqrt{5}+ \sqrt{3}}=\)_____________________________________________
\((2)\)化简:\( \dfrac{1}{ \sqrt{3}+1}+ \dfrac{1}{ \sqrt{5}+ \sqrt{3}}+ \dfrac{1}{ \sqrt{7}+ \sqrt{5}}+…+ \dfrac{1}{ \sqrt{99}+ \sqrt{97}}\).