$\displaystyle \begin{array}{{>{\displaystyle}l}} \sqrt{4a^{2}} =|2a|=2a\ ( với\ a\geqslant 0) \ \\ \sqrt{0.16( x-2)^{2}} =\sqrt{[ 0.4( x-2)]^{2}}\\ =|0.4( x-2|=0.4( x-2)\\ =0.4x-0.8( \ x\geqslant 2) \ \\ c)\sqrt{25( 3-x)^{2}} +3\\ =\sqrt{[ 5( 3-x)]^{2}} +3\\ =|15-5x|+3\ \\ Với\ x\geqslant 3\ thì\ \\ 15-5x+3=18-5x\\ x< 3\ thì\ \\ -15+5x+3=-12+5x\\ \\ d)\frac{1}{2( x-5)}\sqrt{36( x-5)^{2}} -5\\ =\frac{1}{2( x-5)} .|6( x-5|-5\\ +Với\ x\geqslant 5\ thì\frac{1}{2( x-5)} .[ 6( x-5)] -5( x\#5)\\ =3-5=-2\ \\ +Với\ x< 5\ thì\ \\ \frac{1}{2( x-5)} .-[ 6( x-5)] -5\\ =-3-5=-8\ \\ \\ \end{array}$
