a)ĐK : a > 0
A = \(\dfrac{\sqrt{a}\left(\sqrt{a}+1\right)\left(a-\sqrt{a}+1\right)}{a-\sqrt{a}+1}-\dfrac{\sqrt{a}\left(2\sqrt{a}+1\right)}{\sqrt{a}}+1\)
= \(a+\sqrt{a}-2\sqrt{a}-1+1=a-\sqrt{a}\)
b: ĐểA=2 thì a-căn a-2=0
=>a-2 căn a+căn a-2=0
=>căn a-2=0
=>a=4
c: \(A=a-\sqrt{a}+\dfrac{1}{4}-\dfrac{1}{4}=\left(\sqrt{a}-\dfrac{1}{2}\right)^2-\dfrac{1}{4}>=-\dfrac{1}{4}\)
Dấu = xảy ra khi a=1/4