I was half asleep when I posted this, so I didn't actually state what I had a problem with exactly.
When I expressed it in partial fractions, I expressed it as (1/4) / (x+1) instead of (-1/4) / (-1-x).
However, when evaluating it in the integration part, I first left that part out as a log or ln for a negative number does not exist.
Then, after I saw the answer, I tried by taking the -1 out of (x+1). In the end, I ended up with (1/4) ln (81/77).
Now I realise that I left out one tiny thing that messed up my calculations .... the modulus sign