how does
become
i got the completing the squares part but how does it turn to -1 and where did the 2 infront of the second integral come from...
Now splitting the original integral into two pieces, the second one is ready. (Since there's a hidden logarithm there, you may remove the absolute value bars for 'cause it's always positive.) As for the first piece:
and this is an arctangent, let and proceed from there.