Good hard practice data suffiency question I don't get

[houstonrockets16]

If a does not equal b, what is the value of a+b?

1) (a^2-b^2) / (a-b) = 6
2) (a+b)^2 = 36

I understand that 2 is definetly not possible because we get a+b = plus or minus 6

but anyways.. the answer is A

Is there anyway someone can please explain why this is true? I thought the answer was C

Thanks in advance

[deep2002]

From statement one, you can rearrange it as follows:

(a-b)(a+b)/(a-b) = 6

the top and bottom (a-b) terms cancel out leaving you with:
a+b = 6

therefore 1 is sufficient

for statement 2 you get a+b = +/- 6 which gives you 2 answers and therefore it is not sufficient.