Question

 

Mn giúp e câu này vs ạ.

Answer 1

a: ĐKXĐ: a>0; a<>1

\(A=\left(\sqrt{a}-\dfrac{1}{\sqrt{a}}\right)\cdot\dfrac{a}{\sqrt{a}+1}=\dfrac{a-1}{\sqrt{a}}\cdot\dfrac{a}{\sqrt{a}+1}\)

\(=\sqrt{a}\left(\sqrt{a}-1\right)=a-\sqrt{a}\)

b: A=a-căn a+1/4-1/4

=(căn a-1/2)^2-1/4>=-1/4

Dấu = xảy ra khi a=1/4