\(\sqrt{\dfrac{m}{1-2x+x^2}}+\sqrt{\dfrac{4m-8mx+4mx^2}{81}}=\sqrt{\dfrac{m}{\left(1-x\right)^2}}+\sqrt{\dfrac{4m\left(1-2x+x^2\right)}{81}}\\ =\dfrac{\sqrt{m}}{\left|1-x\right|}+\dfrac{2\sqrt{m}\left|1-x\right|}{9}=\dfrac{9\sqrt{m}+2\sqrt{m}\left(1-x\right)^2}{\left|1-x\right|.9}\\ =\dfrac{\sqrt{m}\left(9+2-4x+2x^2\right)}{\left(x-1\right).9}\)
tới đây thì hết bt rồi