C3 Differentiation

I'm stuck on the C3 differentiation question (x + 1)(x - 1)^(1/2)

I used the chain rule on (x - 1)^(1/2) to get 1/2(x - 1)^(-1/2)

and then used the product rule to get

(x + 1)1/2(x - 1)^(-1/2) + (x - 1)^(1/2)

I'm not sure what to do next because the answer should be

(3x - 1)1/2(x - 1)^(-1/2)

but when ever I expand it I can never get this answer.

First part should be:

0.5(X+1)(X-1)^(-0.5) + (X-1)^0.5

Posted from TSR Mobile

The main part I don't understand is where (3x -1) part of the answer comes from?