a: \(\Rightarrow x\left(x+1\right)-2\left(x-1\right)=4\)
\(\Leftrightarrow x^2+x-2x+2-4=0\)
=>(x-2)(x+1)=0
=>x=2
b: \(\Leftrightarrow2x-2\sqrt{x}-3\sqrt{x}+3=0\)
\(\Leftrightarrow\left(\sqrt{x}-1\right)\left(2\sqrt{x}-3\right)=0\)
=>x=1 hoặc x=9/4
c: \(\Leftrightarrow\sqrt{1-x^2}=1-x\)
\(\Leftrightarrow\left\{{}\begin{matrix}x^2-1=x-1\\-1< =x< =1\end{matrix}\right.\Leftrightarrow x\in\left\{0;1\right\}\)