g(x) = x^(1/2) (x + 3) ) 
Apply distributive property:
 x^(1/2 + 1)  + 3 x^(1/2) = x^(3/2) + 3x^(1/2)
Multiply the two functions: 
[x^(3/2) + 3x^(1/2)] * [x - 6] = x^(3/2 + 1) - 6x^(3/2) + 3x^(1/2 + 3/2) - 18x^(1/2)
= x^(5/2) - 6x^(3/2) + 3x^2 - 18x^(1/2)
Order:
x^ (5/2) + 3x^2 - 6x^(3/2) - 18x^(1/2) <--------- answer