It's because of operator precedence. ** has a higher precedence than / in the same way that * has higher precedence thatn +.

You wouldn't expect 3 * 3 + 2 to equal 15 do you?

So similarly your 9**1 / 2 is interpreted as (9**1) / 2. If you mean to raise 9 to the power of 0.5 you need to clarify it as:

9 ** (1/2)