[tex]a=3^{0,5}*3^{-1,25}*3^{0,75}=3^{0,5+(-1,25)+0,75}=3^{0,5- 1,25 +0,75}=3^0=1\\\\b=3^{0,5}*18+3^{2,5}=3^{0,5}* 9*2+3^{2,5}=3^{0,5}* 3^2*2+3^{2,5}= \\\\= 3^{0,5+2} *2+3^{2,5}=2*3^{2,5} =2* 3^{2,5} +3^{2,5} =3^{2,5}*(2+1)=3^{2,5}*3=3^{2,5+1}=3^{3,5}\\\\\frac{b}{a}=\frac{3^{3,5}}{1}=3^{\frac{35}{10}}=3^{\frac{7}{2}}\\\\odp.\ \ \ C[/tex]
