7:
a: \(A=\dfrac{x+2\sqrt{x}+1+x-2\sqrt{x}+1-3\sqrt{x}-1}{x-1}\)
\(=\dfrac{2x-3\sqrt{x}+1}{x-1}=\dfrac{\left(2\sqrt{x}-1\right)\left(\sqrt{x}-1\right)}{x-1}\)
\(=\dfrac{2\sqrt{x}-1}{\sqrt{x}+1}\)
A<1
=>A-1<0
=>\(\dfrac{2\sqrt{x}-1-\sqrt{x}-1}{\sqrt{x}+1}< 0\)
=>căn x-2<0
=>0<=x<4 và x<>1