a.\(\sqrt{\left(2x-1\right)^2}-2x+3\)
\(=2x-1-2x+3=2\)(vì x\(\ge\)1/2 nên 2x-1\(\ge\)0)
b.\(B=\sqrt{\frac{\left(3\sqrt{5}+1\right)\left(2\sqrt{5}+3\right)}{\left(2\sqrt{5}-3\right)\left(2\sqrt{5}+3\right)}}\left(\sqrt{10}-\sqrt{2}\right)\)
\(=\sqrt{\frac{33+11\sqrt{5}}{11}}\left(\sqrt{10}-\sqrt{2}\right)=\sqrt{3+\sqrt{5}}.\left(\sqrt{10}-\sqrt{2}\right)\)
\(=\sqrt{6+2\sqrt{5}}\left(\sqrt{5}-1\right)=\sqrt{\left(\sqrt{5}+1\right)^2}\left(\sqrt{5}-1\right)\)
\(=\left(\sqrt{5}-1\right)\left(\sqrt{5}+1\right)=4\)