\(A=\dfrac{\sqrt{15}-\sqrt{12}}{\sqrt{5}-2}-\dfrac{1}{2-\sqrt{3}}=\dfrac{\sqrt{3}\left(\sqrt{5}-\sqrt{4}\right)}{\sqrt{5}-2}-\dfrac{2+\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}=\dfrac{\sqrt{3}\left(\sqrt{5}-2\right)}{\sqrt{5}-2}-\dfrac{2+\sqrt{3}}{4-3}=\sqrt{3}-\left(2-\sqrt{3}\right)=\sqrt{3}-2-\sqrt{3}=-2\)
Vậy A=-2
căn ký hiệu là v nhé
v15=v3.v5; v12= 2.v3 thay vào có:
A = v3 - 1/(2-v3) = (2v3-3-1)/(2-v3)
= 2(v3-2) / (2-v3) = -2