Giúp mình với !
1. Rút gọn
a)\(\frac{\sqrt{6}+\sqrt{10}}{\sqrt{21}+\sqrt{35}}\)
b) \(\frac{\sqrt{450}+3\sqrt{27}}{3\sqrt{3}+\sqrt{45}}\)
c) \(\frac{\sqrt{2}+\sqrt{3}+\sqrt{4}-\sqrt{6}-\sqrt{9}-\sqrt{12}}{\sqrt{2}+\sqrt{3}+\sqrt{4}}\)
d) \(\frac{\sqrt{6-2\sqrt{5}}}{\sqrt{5}-1}\)