Yes, I realized your point yesterday while on break at work. And that after you square root both sides getting +/-(a-t/2)=+/-(b-t/2) it's the negative of one side that equals the positive of the other since a and b will be equal amounths greater then and less than t/2 since they equal t. I'm not sure how you would show this in the next step of it though, I've never done questions with 2 +/- when I was in school. I would assume you'd then have 4 posible combinations and you'd somehow show that the two showing that a=b are false and the other two simplify to being a+b=t which is of course what you started with. Thanks for all your help figuring this out, and this just reinforced my hatred of quare rooting :P. Just kidding of course.