\(\sqrt{x}=a;a>0\Leftrightarrow A=a^3-3a^2+4a-2\)
\(\Leftrightarrow A=\left(a^3-3a^2+3a-1\right)+\left(a-1\right)\)
\(\Leftrightarrow A=\left(a-1\right)^3+\left(a-1\right)\)
\(A=\left(a-1\right)\left[\left(a-1\right)^2+1\right]\)
\(A=\left(\sqrt{x}-1\right)\left(x-2\sqrt{x}+2\right)\)