Efectuati calculele:

a)[tex] \frac{1}{ \sqrt{2}+1 } + \frac{1}{\sqrt{3}+ \sqrt{2} } + \frac{1}{ \sqrt{4}+ \sqrt{3} }+ \frac{1}{ \sqrt{5}+ \sqrt{4} }= [/tex]
b)[tex]( \frac{1}{ \sqrt{6}+ \sqrt{5} } + \frac{1}{\sqrt{7}+ \sqrt{6} } + \frac{1}{ \sqrt{8}+ \sqrt{7} }+ \frac{1}{ \sqrt{9}+ \sqrt{8} })* \frac{1}{3- \sqrt{5} } = [/tex]