a)\(\sqrt{27.48\left(1-a\right)^2}=\sqrt{3^2.3.4^2.3}.\left|1-a\right|=\sqrt{36^2}.\left(1-a\right)=36\left(1-a\right)\)
b)\(\dfrac{1}{a-b}.\sqrt{a^4\left(a-b\right)^2}=\dfrac{1}{a-b}.a^2\left|a-b\right|=\dfrac{1}{a-b}.a^2.-\left(a-b\right)\)\(=\)\(-a\)2