Question

1) Thực hiện phép tính:

a) A= \(\sqrt{243}\) -\(\sqrt{27}\)+ \(\sqrt{3}\) -\(\sqrt{48}\)

b) B= \(\dfrac{5+\sqrt{5}}{\sqrt{5}}\) +\(\dfrac{3+\sqrt{3}}{\sqrt{3}+1}\) -(\(\sqrt{3}\) + \(\sqrt{5}\) )

Answer 1

\(A=\sqrt{243}-\sqrt{27}+\sqrt{3}-\sqrt{48}\\ =\sqrt{81\cdot3}-\sqrt{9\cdot3}+\sqrt{3}-\sqrt{16\cdot3}\\ =9\sqrt{3}-3\sqrt{3}+\sqrt{3}-4\sqrt{4}\\ =\left(9-3+1-4\right)\sqrt{3}\\ =3\sqrt{3}\)

\(B=\dfrac{5+\sqrt{5}}{\sqrt{5}}+\dfrac{3+\sqrt{3}}{\sqrt{3}+1}-\left(\sqrt{3}+\sqrt{5}\right)\\ =\dfrac{\sqrt{5}\left(\sqrt{5}+1\right)}{\sqrt{5}}+\dfrac{\sqrt{3}\left(\sqrt{3}+1\right)}{\sqrt{3}+1}-\sqrt{5}-\sqrt{3}\\ =\sqrt{5}+1+\sqrt{3}-\sqrt{5}-\sqrt{3}\\ =1\)