Answer :
Let [tex]y=ab^x,[/tex] as described in the problem statement. Plugging in [tex]x=2[/tex] and [tex]x=5[/tex] gives us the equations [tex]18=ab^2[/tex] and [tex]60.75=ab^5.[/tex] Since [tex]a,b[/tex] are nonzero, we divide the second equation by the first to get [tex]\frac{27}{8}=b^3,[/tex] which means that [tex]b=\frac{3}{2},[/tex] after taking the cube root. Plugging this value for [tex]b[/tex] into the first equation, we now have [tex]18=a(3/2)^2=\frac{9a}{4}.[/tex] Solving gives [tex]a=8,[/tex] and our desired exponential equation is [tex]\boxed{y=8\left(\frac{3}{2}\right)^x}.[/tex]