Wolfram Alpha computation of exponents

Question

I am a bit confused by a Wolfram Alpha. In my calculations I had a term like $x^{(3/2)}$ which I wrote as $\sqrt{x^3}$. As silly mistakes happen quite often to me, I often double check stuff like this by typing $x^{(3/2)}-\sqrt{x^3} $ into Wolfram Alpha with the expecation to see $0$. The result, which I uploaded here, did surprise me though.
Can someone explain what is going on?
I suspect that the two terms are being calculated numerically in different ways, which leads to slight differences.