\(a,\dfrac{x-\sqrt{x}}{\sqrt{x}-1}\) \(\left(dk:x\ge0,x\ne1\right)\)
\(=\dfrac{\sqrt{x}\left(\sqrt{x}-1\right)}{\sqrt{x}-1}\\ =\sqrt{x}\)
\(b,\dfrac{1-2\sqrt{x}+x}{1-\sqrt{x}}\left(dkxd:x\ge0,x\ne1\right)\)
\(=\dfrac{1^2-2\sqrt{x}+\sqrt{x^2}}{1-\sqrt{x}}\\ =\dfrac{\left(1-\sqrt{x}\right)^2}{1-\sqrt{x}}\\ =1\)