Mark scheme underlining

I just did this past paper, and something on the mark scheme caught my eye. In question three, they underline several phrases (link below to the mark scheme). When they do that, does that phrase need to be seen at all for the method? I only put down:

(x - 10)² + (y - 8)²

Not:

(x +- 10)² + (y +- 8)²

Would that affect me?
I can include the problem and working if necessary.
http://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2013/Exam%20materials/6664_01_rms_20120816.pdf

No, what the markscheme means by $\pm$ is that the candiate gets the mark if they put either plus or a negative. i.e: they are being lenient. They will give the mark even if the candidate puts the wrong sign in the bracket but as long as they get the numbers correct. You would most definitely get the mark for what you've written. You're underestimating the leniency of the markscheme, in my opinion - from what I've seen of your questions. They are more lenient than you think they are.

OK, that's what I thought. Anything important about the underlining, though?

The underlinging means it has to be seen to get the mark.

Thank you very much!