How can I convert 5^(3/2) to 5* 5^(1/2)



hello:

I hope expand (a+b sqrt(5))^n  to the form  A+B sqrt(5), but expand
((1+sqrt(5))) give me 5^(3/2)+ 3 sqrt(5) + 16. How can I convert 5^(3/2) to
5 5^(1/2) ?

thanks

z.x.l