Rút gọn: a) căn 6 - căn 15/căn 35-căn 14 b) 5+căn 5/ căn 10+căn 2

`a)`

`(\sqrt{6}-\sqrt{15})/(\sqrt{35}-\sqrt{14})`

`=(\sqrt{3}(\sqrt{2}-\sqrt{5}))/(\sqrt{7}(\sqrt{5}-\sqrt{2}))`

`=(-\sqrt{3})/(\sqrt{7})=(-\sqrt{21})/7`

`b)`

`(5+\sqrt{5})/(\sqrt{10}+\sqrt{2})`

`=(\sqrt{5}(\sqrt{5}+1))/(\sqrt{2}(\sqrt{5}+1))`

`=(\sqrt{5})/(\sqrt{2})=(\sqrt{10})/2`