[Toán 9]Chứng minh

E

eye_smile

a,$(\sqrt{10}-\sqrt{2})(3+\sqrt{5})\sqrt{3-\sqrt{5}}=(3+\sqrt{5})(\sqrt{5}-1)\sqrt{6-2\sqrt{5}}=(3+\sqrt{5})(\sqrt{5}-1)^2=\dfrac{(\sqrt{5}+1)^2.(\sqrt{5}-1)^2}{2}=\dfrac{16}{2}=8$

b,$\dfrac{1}{\sqrt{n+1}-\sqrt{n}}=\dfrac{1}{\dfrac{1}{\sqrt{n}+\sqrt{n+1}}}=\sqrt{n}+\sqrt{n+1}$
 
Last edited by a moderator:
You must log in or register to reply here.
Top Bottom