\(\left(3x+1\right)^2=25.4\\ < =>\sqrt{\left(3x+1\right)^2}=\sqrt{100}< =>3x+1=10\\ < =>3x=9\\ < =>x=3\\\)

1,c

2,d

a,Mg+2HCl=>MgCl2+H2

b,nHCl=0,05.3=0,15(mol)

nMg=12/24=0,5(mol)=>Mg dư, tính thao HCl

nH2=1/2 nHCl=0,075(mol)

=>VH2=0,075.22,4=1,68(l)

c,nMgCl2=nH2=0,075(mol)

mMgCl2=0,075.95=7,125(g)

\(a,2\sqrt{18}-4\sqrt{50}+3\sqrt{32}\\ =6\sqrt{2}-20\sqrt{2}+12\sqrt{2}=-2\sqrt{2}\\ b,\sqrt{\left(\sqrt{8}-4\right)^2}+\sqrt{8}\\ =4-\sqrt{8}+\sqrt{8}\\ =4\\ c,\sqrt{14-6\sqrt{5}}+\sqrt{6+2\sqrt{5}}\\ =\sqrt{\left(3+\sqrt{5}\right)^2}+\sqrt{\left(\sqrt{5}+1\right)^2}=3+\sqrt{5}+\sqrt{5}+1\\ =4+2\sqrt{5}\)